Chapter II: Part 2

Every part of the 590-acre Reservation is used to some extent by blue racers living on this area. Home ranges of most individuals are so large as to include a variety of habitats, both woodland and grassland. The habitat preferences vary according to season. In autumn some racers migrating to rock ledges to hibernate are found in mesic forest, but at that time of year leaves have begun to fall and the forest floor is less dark and humid than in summer. In spring also racers not yet back on their summer ranges are often seen either along the hilltop ledges, or moving downhill through woods toward bottomland meadows. However, in summer, the finding of a racer in mesic woodland is a rare event. Occasionally the snakes make trips across such blocks of woodland hundreds of feet wide, but they do not linger in the woodland. In decreasing order of preference the habitats used by racers on my study area may be classified as follows:

1. Tall-grass prairie, (Plate 22) either original or regenerated, dominated by native perennial grasses in stands three feet to seven feet high, including big blue-stem (_Andropogon gerardi_), little blue-stem (_A. scoparius_) Indian grass (_Sorghastrum nutans_), and switchgrass (_Panicum virgatum_).

2. Pastureland, with introduced brome grass (_Bromus inermis_) and associated weedy vegetation.

3. Brush, in ravines, at woodland edge, and in riparian thickets.

4. Weedy fields, dominated by such pioneer plants as ragweeds, sunflowers, horseweed, milkweed, wild lettuce, aster and goldenrod.

5. Open type of woodland dominated by such trees as honey locust and osage orange.

These habitat types are interspersed on the study area, and each racer has a wide choice of habitats without travelling beyond the limits of its own chosen area.

Grassland that has been closely grazed, mowed or burned does not provide entirely adequate food or shelter, and under such conditions clumps of brush or other dense vegetation may be of critical importance. Throughout the racer's extensive range, fields of grain and hay at times provide suitable habitat, and may support large populations, but in spring, before the young cultivated plants have made much growth, or later in the season, after they have been cut, the racer may need to depend on adjacent areas of pasture, thicket, or woodland edge and the availability of such refugia to a large extent determines the numbers of racers on cultivated areas.

Temperature Relationships

In the locality of my study racers spend approximately half the year in winter dormancy. Earliest spring records and latest fall records for 13 years are shown in Table 4. The spring records in nearly all instances pertain to snakes found in the open or beneath flat rocks warmed by sunshine, usually at or near the rock ledges where hibernation occurs. Juveniles are especially well represented in these earliest spring records, and it seems that they tend to emerge a little earlier, on the average, than the adults, either because they have hibernated in more superficial and less well insulated situations or because their lesser body mass permits more rapid warming to activity than can occur in the adults. The latest fall records all pertain to racers trapped along the rock outcrops, and none was a young of the year.

Table 4. Earliest and Latest Recorded Annual Dates When Blue Racers
Were Active on the Reservation or Rockefeller Tract

==========+==========+=============++==========+==========+============
| Earliest | Latest || | Earliest | Latest
Year | spring | fall || Year | spring | fall
| record | record || | record | record
----------+----------+-------------++----------+----------+------------
1950 | April 16 | November 4 || 1957 | April 30 | November 2
1951 | April 19 | November 13 || 1958 | April 25 | November 20
1952 | April 23 | November 12 || 1959 | April 6 | November 10
1953 | April 8 | November 12 || 1960 | April 22 | November 6
1954 | April 20 | November 12 || 1961 | April 19 | November 1
1955 | April 15 | November 2 || 1962 | April 23 | October 27
1956 | May 11 | November 14 || | |
----------+----------+-------------++----------+----------+------------

Most of the population undoubtedly emerged somewhat later than the average date of April 16 indicated by the records in Table 4, and retired somewhat earlier than the average date of November 8. However, a small percentage of the population probably emerged even earlier each year than my records indicate, and retired into hibernation later than my records indicate. In a typical year, temperatures in April and early May are only occasionally above the level at which racers are able to become active, but are below this threshold most of the time. The same statement applies to an autumn period of late October and November. Most racers are dormant in their hibernacula during these transitional periods of spring and autumn, but some--those that have emerged early in spring, or those that have not yet retired (in fall)--retreat to temporary shelters and revert to a semi-torpid state when temperatures fall below the critical level.

Fig. 3 shows the relative extent of activity along the hilltop outcrops, as reflected by numbers of racers caught at different times during the autumn. Data from 14 years are combined, and the large composite sample indicates that in an average year there is relatively little activity along the hilltop outcrops in early September, but that activity rapidly increases to a peak in mid-October and then tapers off rapidly, usually ending in mid-November, but occasionally ending as early as late October or as late as late November.

The racers recorded in traps had, in many instances, been confined in them for from one to three days before they were found. For any one year records are not sufficiently numerous to show the trend as well as Fig. 3, but Fig. 4 shows year-to-year differences; 1958 was a fairly typical year, and also was the year in which the largest sample was obtained; in 1949 the largest catches were made earlier than usual, and the racers retired early into hibernation; in 1954 warm weather persisted until unusually late in autumn, and racers remained active beyond the time when they ordinarily would have been hibernating; in 1955 and 1961 the most concentrated activity along the outcrops, as reflected by day to day catches, came later than usual, but unseasonably cold weather ended all activity abruptly, earlier than usual.

The racer's annual cycle of activity is, of course, controlled primarily by the weather, and is much delayed or accelerated in some years. But certain stabilizing factors cause the racer's annual cycle to be less variable than that of the weather. For example, in spring when persistently cool weather delays emergence from hibernation beyond the normal time, the increasing azimuth of the sun, and more intense sunshine cause the soil to warm, despite low air temperature, until emergence is finally triggered. Having once emerged, the racer is able to control its bodily temperature to a large extent by basking in sunshine to gain warmth, or by seeking shade or underground shelter to escape overheating. By such behavioral thermoregulation extremes of weather are neutralized, or at least buffered to some degree.

In the course of my study no racers were found in their actual hibernacula. Insofar as known, these were always in deep crevices in strata of limestone near hilltops, and were inaccessible except by removal of the solid rock. The crevices where racers hibernate are known to be several feet deep in some instances, extending well below the frost line. Periodic temperature readings in two such crevices at depths of 12 inches and 30 inches, taken in the winter of 1954 (Fitch, 1956:471) showed that temperatures during dormancy are usually well within the range 0°C to 10°. Whether the racers congregate in hibernating masses in regular "dens" on the Reservation has not been definitely determined, but if so, most of the hibernating groups must be small, because those trapped along the ledges are well scattered, and, in fact, give the impression of being rather uniformly distributed along them. However, ledges of northward exposure are not used as hibernation sites, so far as known, and those of full southward exposure are perhaps preferred, especially where the hilltop has a southward projecting spur, and the exposed rock face is extensive, with many cracks and fissures. I have been unable to detect differences in types of hibernation sites preferred between the racer and the copperhead, which is somewhat more numerous on the same area.

Several authors have contributed to knowledge of hibernation in the racer. Boyer and Heinze in Missouri (1934:195) noted that blue racers often were associated with copperheads in the vicinity of places chosen for hibernation. Burt (1935:329) in Kansas found blue racers emerging from dens among rocks on a prairie hillside, associating with other snakes, _Diadophis punctatus_, _Elaphe guttata_, and _Pituophis melanoleucus_. In the Chicago region, Pope (1944:173) reported scores of blue racers aggregating in October on and around a sand dune with oak woodland. In Ohio, Conant (1938:55) found three blue racers hibernating together about three feet underground in a small hole. One found at another locality had apparently hibernated in company with a massasauga (_Sistrurus catenatus_). In Maryland Cohen (1939:137) saw racers (_C. c. constrictor_) in the act of emerging from an old vole burrow that was a communal hibernaculum, on April 6, 8, and 10. Air temperatures at the time of emergence were 12.5° and 18.5° Centigrade. In Illinois, Schroder (1950:1-2) found seven blue racers hibernating in masses, intertwined with each other and with bull snakes at depths of 36 inches and 42 inches in an abandoned mammal burrow in a sand dune area in early February.

In the course of routine field work I often carried a Schultheis quick-reading thermometer, and from time to time I had opportunities to take the body temperatures of blue racers newly captured by hand. The trend of these records indicated the temperature range within which the snakes normally limit their activity, and the preferred temperature. In an earlier publication (Fitch, 1956:459-460) based on a few more than half the number of records of temperature now available, I discussed responses of the blue racer to temperature. The newer data bear out the trends previously revealed; of 60 records, 39 are within the six-degree range from 29° to 35°, and records are most concentrated in the one-degree range, 34° to 35°. Racers were found active at air temperatures between 15.5° and 32.4°, with the greatest concentration between 26° and 27°. Compared with most other kinds of North American snakes, the racer is remarkably tolerant of heat, and often is several degrees warmer than the level that those of other genera will normally tolerate. Racers have been seen crawling in the sunshine, or basking on days that were uncomfortably hot for humans. For example, on August 28, a large female racer released from a trap was followed and her behavior observed; after crawling some 50 feet through the grass she climbed from a ditch bank onto sunflower stalks and elm saplings, and came to rest among the stalks, in a spot strategically situated for catching grasshoppers. More than half her body was exposed to sunshine and air temperature was slightly above 34° Centigrade, yet the snake showed no sign of discomfort, and for the several minutes that she was kept under observation, did not attempt to withdraw into the shade.

At the Harvey County study area, bodily temperatures were recorded in many of the racers that were caught in traps. These records are much less significant than the records obtained from racers caught by hand and promptly checked for bodily temperatures. The temperatures of the trapped snakes may, to a large extent, reflect the temperatures of air and soil at the time. However, despite their confinement, the trapped racers probably were able to exercise some control over their temperatures by shifting from shade to sunshine, or from the top of the trap to its bottom, where they would be in contact with the substrate. In most of the racers removed from traps, as in those caught by hand, bodily temperatures were somewhat above air temperatures, but the difference was less in the former group of snakes. Figure 8 shows the bodily temperatures of these snakes removed from traps. Occasionally racers died in the traps from overheating. On July 2, 1960, each of two racers in traps had temperatures of 39.4°. One of these was especially vicious and frantic in its attempts to escape, but otherwise seemed unharmed. The second racer was dead, seemingly having succumbed just before it was found. Probably prolonged exposure to temperature in excess of 39° would always result in death of the snake. Racers and other snakes that had become overheated in the traps and were nearing exhaustion had a characteristic limp feel when they were handled. In June, 1960, heat tolerance of a halfgrown racer was compared with that of several other snakes including a copperhead, garter snakes, and ringneck snakes. Each snake in turn was enclosed in a plastic tube plugged with cotton at one end, the snake having a quick-reading thermometer taped in place for a rectal reading. The tube was then placed in sunshine. Over periods of minutes the enclosed snake passed through a characteristic cycle. Soon it would begin to register discomfort as its temperature rose rapidly. Its struggles would become increasingly violent, then would cease abruptly. The snake would suddenly collapse, its body mostly limp, but knotted in slow contortions, its mouth gaping widely. Within a few seconds all movements would cease, but in each instance the seemingly dead snake was soon revived by holding it in cold running water. The copperhead, garter snakes, and ring-necked snakes all collapsed at temperatures near 41°. At this same temperature the racer showed signs of acute discomfort, but did not collapse even after many minutes of exposure. Probably more protracted exposure at this level would have been fatal to the racer as well as to the other kinds tested.

Home Range and Movements

Blue racers that were recorded on more than one occasion were rarely caught again at the original location. For different individuals, distances between capture points ranged from zero up to a little more than three-fourths of a mile. The area of concentrated study was a mile and a half in greatest diameter; there was scant opportunity for capturing racers that moved greater distances. Even those that moved as far as a mile would have passed beyond the boundaries of the study area in most instances. Many of the marked racers that disappeared from my records probably moved beyond the limits of the study area. Nevertheless, in the great majority of instances, the distances between successive capture points for the same individual were relatively short, indicating that each racer tends to remain permanently in a restricted area.

Most captures were made in the type of grassland or brush that provides favorable habitat for the racer during the season of activity, but many other captures were made in woodland along the rock ledges where the snakes come to hibernate. Four different types of movement may be recognized: 1) those in the rock ledge area where hibernation occurs; 2) those between the area where the summer is spent and the hibernation ledge--an actual small scale seasonal migration which takes place in spring and autumn--3) those within a home range, which are part of the day-to-day activities of the racer, and, 4) wandering movements by which the racer shifts its activities, perhaps permanently, from one area to another. In the records of any one snake these different types of movements cannot always be sorted with certainty. Each type will be discussed separately.

Relatively few movements along the ledges were recorded. It seems that having migrated to a ledge, the racer promptly finds its hibernaculum and retires for the winter. In spring there is equally prompt scattering of the emerging racers, which no longer find the ledge attractive. Most recorded movements along the ledges were short. Of 76 movements, nine exceeded 1000 feet, and only four others exceeded 500 feet. Most of the shorter movements were recorded within an autumn season, but several were recorded after the lapse of one or more seasons of activity. The longer movements were as follows: 1250 feet after 8 seasons (male); 1300 feet after three seasons (female); 1600 feet after one season (female); 2000 feet after one season (female); 2280 feet after seven seasons (male); 2200 feet in same season (female); 2410, 2600, and 3200 feet, each after one season (all males). The trend of these records suggests that the tendency to return year after year to the same hibernaculum is not strong; after using one for a period of years, the racer may abandon the stretch of ledge and, starting out in the opposite direction from its summer range, find a new hibernaculum as much as half a mile from the old one. Records of distances between capture points on the ledges for individual racers are shown in Fig. 12.

A total of 124 movements between summer ranges and ledges were recorded, and the distances averaged 1309 feet--approximately a quarter mile. Some racers living in hilltop fields may have had home ranges that included rock ledges, or at least were adjacent to them. In such instances no seasonal migrations would have been necessary to reach hibernacula in the autumn and summer ranges in the spring. Several short movements--100 feet, 150 feet, and 200 feet--can be explained on the basis that home ranges and hibernation ledges overlapped or were near at hand, but most of the movements were longer. The longest movement was 4020 feet, after a lapse of four seasons. Twenty-four movements exceeding 2000 feet were recorded. For these the intervals between captures averaged more than double the time for the remaining movements, indicating that the longtime permanent shifts were involved in many instances.

For all the racers living in bottomland, ranges were separated from ledges by areas of wooded hillsides averaging approximately 700 feet across. These relatively unfavorable areas had to be traversed in the course of the semi-annual migrations. Even some of the racers that lived in hilltop fields apparently crossed wooded slopes in order to reach distant hibernation ledges, or else each reached the ledge by a roundabout route although it could have found a ledge much nearer its summer range. For the 124 ledge-to-field and field-to-ledge movements, the median distance was 1030 feet. The sexes were almost equally represented in this sample but the average distance for the 55 males--1425 feet--notably exceeded that for the 69 females--1220 feet. These movements are shown in Fig. 9.

McCauley (1945:76) in Maryland described what seemed to be incipient territoriality in a large male racer that remained several hours in a small area, crawling about conspicuously with head raised, seemingly on patrol. When an even larger male racer intruded, the first one aggressively drove him away, but neither paid any attention to a king snake that was also on the area. Other authors have noted the attachment of a racer to a small familiar area. Conant (1938:53) wrote that many of the racers he saw sought shelter in definite retreats. One of these racers was seen resting on top of a brush pile four times in a single afternoon, and each time it followed the same route to the same inaccessible spot beneath the brush.

My own observations do not bear out the idea that racers maintain regular territories, since several males may be present within a small area, even in the breeding season. Hostile behavior between males has not been observed by me under natural conditions, and in confinement has been seen only in instances of self defense. Like the racer Conant observed on a brush pile, individuals may linger in the vicinity of a favored shelter or foraging area for periods of hours, but such associations are ephemeral, and soon the snake moves on. In a uniformly favorable habitat a racer may cruise about freely in tall grass or brush. Individuals that I have attempted to follow, after flushing them or releasing them from traps, often covered distances of 100 to 300 feet within periods of a few minutes before I lost them. In such instances I maintained sufficient distance between myself and the snake so that the latter was not actively escaping. Probably the snake was not aware of pursuit in most instances, although I was able to glimpse it through the stems of grass, weeds, or shrubs, or was informed of its course by the swaying tops of grass and other vegetation.

For many of the racers captured over periods of years it was possible to plot "minimum home ranges" in the areas that they occupied. One caught 12 times in five consecutive years will serve as a typical example. There were seven locations involved; three captures were made at one point and two captures at each of two others; the other five locations were each represented by a single capture. One of the seven locations was for a capture made at a rock ledge in October, and hence can be eliminated from considerations of home range. The other six locations are based upon captures made from late May to early August, and they form a rhomboid pattern, with three locations in alignment on one side and two others inside the quadrangular figure formed by the five outlying points. Obviously such a group of records gives some idea of the location and extent of the snake's activities but the information is far from complete. As shown by Odum and Kuenzler (1955), a much larger series of records, usually several dozen, with eight or more marginal locations, is necessary to illustrate even an approximation of the actual home range. Under the conditions of my study such a series of records was unattainable. Few if any of the racers recaptured had more complete series of records than the one mentioned above.

For 20 racers the records were sufficiently numerous and well distributed to permit plotting of minimum home ranges. One of these ranges was hexagonal, nine were pentagonal, eight were rhomboidal and three were triangles. In four instances the area encompassed was broken by woodland, indicating that the home range comprised two or three disjunct segments. In all instances the smaller segments were triangular. The 20 minimum home ranges averaged 6.6 acres (3.2 to 12.8). The 15 ranges of males averaged 7.3 acres, whereas the five ranges of females averaged only 4.5 acres, but the sample is too small to be relied upon for differences in the sexes.

In an earlier publication (Fitch, 1958:73) I discussed an alternative method for determining size of home range in animals that move about freely within a chosen area, not having their movements restricted by attachment to a specific home base. Ordinarily any two records of the animal within its home range will be separated _on the average_ by a distance equal to half the diameter of the area. Assuming that home ranges in general tend to have a circular shape, except as restricted by limiting environmental factors, the area can be easily computed from the average recorded movement--the home range radius. It is necessary, of course, to have a sufficiently large number of records of movements to obtain an average that is statistically reliable.

A major problem is that of recognizing movements that involve an extension of the original range or a shift away from it to a new area. A few exceptionally long movements were recorded. If these are included in the computations of home range, they greatly increase the average distance, probably introducing error. Also, the number of exceptionally short movements was greater than might have been expected if all locations of capture are at random to each other. In some instances a racer newly released may have blundered into the same trap again, or into the trap at the opposite end of its drift fence. In other instances traps may have been so strategically situated with respect to preferred travel routes that they caught the same snakes repeatedly. In still other instances, the range of an individual might have been mostly outside the study area, with only one end or corner overlapping the trap sites.

A total of 471 records for consecutive captures in field areas is available, 305 for males and 166 for females. In 20 instances successive sites of capture were the same and movement was recorded as zero. Of the 471 records, 207 involved a relatively long time span, including at least one hibernation period; the remaining 264 were based upon successive records within the same season of activity. The trends were much the same in the records involving a longer time span (up to four years) as in those records involving captures made in a single season, but for the longer periods there were some exceptionally long movements, and relatively few short movements of less than 100 feet.

Records of male racers and those of females were used for separate computations. For each series, the ten per cent of movements that were longest and the ten per cent that were shortest were eliminated from consideration in calculation of the average distance between points of capture. For the remaining 244 records of males an average movement of 595 feet was calculated, and for 132 records of females an average movement of 574 feet. These distances, if accepted as typical home range radii, would represent home ranges of 26.3 acres for males and 23.8 for females. In an earlier discussion of spatial relationships in the racer (Fitch, 1958:119), based upon relatively scanty data, I estimated the home range to be approximately 23 acres in males. But with only nine records for female racers I calculated the home range to be 9.7 acres.

The disparate figures obtained from plotting minimum home range and from calculating average home range radius are not irreconcilable, since a minimum home range based on only four or five points would ordinarily include only a fraction of the actual range. Distances up to 1500 feet are included in the calculation of home range. It seems that home ranges often have a diameter of this magnitude or a little larger, although the estimated average diameter is 1140 feet. Home ranges probably most often deviate from circular shape to form an ellipse, with one diameter markedly exceeding the other. Woodland, water, roads, buildings, or cultivated fields, or other areas that are unfavorable or uninhabitable often form the boundary of a home range and influence its shape.

Many of the longer movements constituted clear-cut shifts in range. In one exceptional instance a large adult female captured in the northeastern part of the Reservation on June 22, 1950, was released 21 days later at a point 3900 feet southwest of the place of capture. On May 27, 1960 she was caught within 600 feet of the original location, seemingly having made a homing movement. Among the nine racers recorded to have made longest movements (exclusive of those movements made to or from hibernacula) four were recorded also to have made later long movements in the reverse direction, probably returning, each to its original home range, although in every instance the return movement was somewhat less than the original. A female of two-year-old size when first captured on September 2, 1957, was recaptured 3100 feet southeast on May 10, 1958. On August 7, 1959, she was recaptured again 2400 feet from the second location in the direction of the original capture. Similarly, in a three-year-old female a shift of 2730 feet was recorded at the second capture after 21 months, and at the third capture 14 months after the second, a return trip of 2360 feet had been made. A second-year female made a trip of 2640 feet between May 17 and October 1, 1960; by May 1961 she had returned 2000 feet to the vicinity of her original capture. From one year to the next an adult male shifted 2450 feet; after another year he had moved back 1550 feet. Most of the longer movements recorded were those between home ranges in fields and hibernacula along ledges, but in this class of movements, distance was somewhat proportional to elapsed time. For 59 such movements exceeding 2000 feet the average was 3.1 years, whereas for 114 field-to-ledge movements of less than 2000 feet, average elapsed time was 1.6 years. This trend suggests that over periods of years a racer is likely to shift its range or its hibernaculum or both.

Average elapsed time between captures was 7.7 months. In the 471 field-to-field movements recorded, 53--slightly more than eleven per cent--exceeded 1500 feet and can reasonably be considered shifts of home range. The average elapsed time between captures for this group of snakes was 9.5 months. The evidence suggests that, even in an area of favorable habitat, somewhat more than ten per cent of the racers in a population annually shift their home ranges somewhat, but that many stay in the same home range for periods of years or perhaps throughout life.

Shifts in range were especially noticeable where availability of suitable habitat underwent seasonal change. Along the north edge of the Reservation, prairie adjoined cultivated fields where grain or hay was grown. Until late May, the cultivated crops made little growth and the fields were almost bare. They provided insufficient shelter for the racers, which tended to keep to the prairie, where old grass of the previous year's growth furnished them with ample cover. Later in the season, crops, of oats, wheat, and alfalfa constituted suitable cover for the racers, and many of them shifted their ranges to the cultivated fields, but corn and milo crops were much less adequate for their needs. After harvesting of crops, cover in the fields was again inadequate for the racers' needs, and they tended to retreat to edge situations, or to adjacent prairie.

Food Habits

_Methods of Obtaining Prey_

The racer hunts by stealth, but actively, obtaining its prey by keen eyesight and swift movements. Wright and Bishop (1915:160) wrote that because of its great speed it can catch anything that moves on the ground. As a racer moves stealthily through dense vegetation, its dull, uniform dorsal color blends well with the surface litter of dead plant material. In prowling, the snake glides along rapidly and alertly, in a jerky fashion, with frequent momentary pauses and changes of direction. Because of its inconspicuousness, it is not likely to be detected by the prey until it is close at hand. The snake is ready to dash in pursuit of any small animal that flies, jumps or runs to escape.

On August 27, 1955, my daughter observed a large racer hunting among tall weeds at the edge of the pond on the Reservation. Several times in the course of its movements, it flushed small frogs (_Rana pipiens_) and each time the snake darted in unsuccessful pursuit of the rapidly hopping frog. On several occasions I have been led to a blue racer by the distressed croaking of a frog that the snake had captured. In each instance, despite my cautious approach, the racer saw me before I detected it, and then darted away, abandoning its prey. On one occasion, while I was still a few yards from the racer, and before the latter had detected me, the frog broke free and hopped away rapidly through tall grass and weeds, and after several leaps, hid, concealed by dense screening vegetation. The racer darted in pursuit but could not find the frog. For several minutes the snake persisted in an active search; with forebody elevated and head held high, it would turn first in one direction and then in another, with nervous, jerky movements, obviously keyed up to a high pitch of excitement. Then it became aware of my presence, lowered its head, and glided away rapidly, abandoning the search.

Although the racer depends to a large extent on sight to find its prey, scent may play some part also, as indicated by the presence in the food of young mammals taken from nests, some probably found underground. Near Garnett, Kansas, on May 4, 1952, Richard B. Loomis found a racer attacking a collared lizard (_Crotaphytus collaris_) beneath a large flat rock. The lizard was retaliating by biting the snake's neck. The posterior part of the snake protruded into the open, and its thrashing had directed the attention of the observer to it. Whether the racer first found the lizard under the rock, or followed it there after flushing it in the open is unknown.

An encounter between a large blue racer and an adult Great Plains skink (_Eumeces obsoletus_) on August 30, 1948, was described as follows: "The skink, grasped by one flank, had twisted back and seized the skin of the snake's neck in a bulldog grip, and they lay interlocked, motionless except for their rapid panting, and occasional straining of the skink to bite harder or of the snake to shift its grip and work its jaws toward the skink's head. The racer broke the skink's grip, and began to swallow it head first. When only the hind legs and tail of the skink still protruded from the racer's mouth, I lunged forward in an attempt to catch both reptiles. With a sudden movement the snake disgorged the skink, which darted away into the grass and escaped" (Fitch, 1955:78).

_Composition of Food_

Many authors have contributed to knowledge of the racer's food habits. In most instances the records have been few or casual, but several intensive studies have been made, notably by Surface (1906) in Pennsylvania, Ortenburger (1928) for the species as a whole, Uhler, Cottam and Clark (1939) in Virginia, Clark (1949) in Louisiana, Auffenberg (1949) in southern Texas, Hamilton and Pollack (1956) in Georgia, and Klimstra (1959) in southern Illinois. However, the findings of different authors are not strictly comparable; some have made general statements concerning the food habits but have mentioned specific items only when these were considered unusual. Certain authors have listed individual prey animals eaten; others have indicated the percentages (in bulk or in frequency) that the different kinds of prey comprised. Some writers have identified food animals only in broad categories such as "insect," "beetle" or "snake" while others have undertaken specific determinations for all the prey or for certain taxonomic groupings that were subjects of special interest.

For the eastern black racer (_C. c. constrictor_) the following food items have been recorded: 1 robin (_Turdus migratorius_, Storer, 1839:226); 1 copperhead (_Agkistrodon contortrix_, Verrill, 1869:158); 1 weasel (_Mustela_ sp.--presumably the diminutive _M. rixosa_--Atkinson, 1901:148); 3 undetermined mammals, 1 rabbit, 1 undetermined mouse, 7 voles (2 _Microtus_ sp., 4 _M. pennsylvanicus_, 1 _Clethrionomys gapperi_), 1 undetermined bird, 2 robin eggs, 2 garter snakes (_Thamnophis sirtalis_), 1 water snake (_Natrix sipedon_), 1 grass snake (_Opheodrys vernalis_), 1 green frog (_Rana clamitans_), 1 wood frog (_R. sylvatica_), 1 grasshopper (_Melanoplus femur-rubrum_) 2 camel crickets (_Ceuthophilus_ sp.), 5 moths (cecropia, regal, imperial), 4 beetles, 1 currant worm, 1 ichneumonid wasp (_Nematus ribesii_), 1 currant worm (Surface, 1906:170); 1 ribbon snake (_Thamnophis sauritus_, Ditmars, 1907:282); 3 snakes (1 _Liopeltis vernalis_, 1 _Storeria occipitomaculata_, 1 undetermined), 6 white-footed mice (1 _Peromyscus leucopus_, 5 _P. nuttalli_), 1 vole (_Microtus pennsylvanicus_), 16 crickets (9 _Gryllus pennsylvanicus_, 4 _G. assimilis_, 2 _Miogryllus verticalis_, 1 _Nemobius fasciatus_), 2 grasshoppers (_Dissosteira_ sp.), 1 lepidopteran, 3 elaterid beetles (Ortenburger, 1928:200). Richmond and Goin (1938:310) recorded finding the stomach of a black racer crammed with June beetles (_Phyllophaga_). Conant (1938:53) recorded a black racer from Ohio that had a smaller individual of its own species in its stomach. The smaller snake contained a caterpillar. Uhler, Cottam and Clark (1939:34) found food in 16 of 34 black racers from Virginia. Mammals, including a shrew (_Blarina brevicauda_), a mole, a flying squirrel (_Glaucomys volans_), a microtine, and a mouse (_Peromyscus_ sp.) made up 26 per cent, 2 worm snakes (_Carphophis amoenus_), 2 ring-necked snakes (_Diadophis punctatus_), and 1 water snake (_Natrix sipedon_) made up 25.6 per cent, 5 birds including a warbler and a sparrow, made up 17.75 per cent; 2 frogs (_Rana_ sp.) made up 9.38 per cent, 1 fence lizard (_Sceloporus undulatus_) made up 6.25 per cent, and insects, including cicadas (_Tibicen_ sp.) and larval lepidopterans, made up 15.09 per cent. In Indiana, Minton (1944:457) examined 11 food-containing stomachs; there were rodents in six, snakes in five, a tree frog in one, and insects (cicadas, large grasshoppers) in four, and another black racer was found swallowing a small box turtle (_Terrapene carolina_). In Maryland, McCauley (1945:75) examined eight digestive tracts and recorded a shrew (_Blarina brevicauda_) in one, an unidentified mammal in one, 2 small cicadas in one, 2 small chickens in one, a fence lizard (_Sceloporus undulatus_) in one, and frogs and toads (including _Hyla crucifer_) in one; a ninth snake had eaten a half grown rat. In Connecticut, Finneran (1948:124) observed a large black racer eating a 21-inch garter snake (_Thamnophis sirtalis_). Duellman (1951:338) recorded a black racer in Greene County, Ohio, swallowing a large garter snake (_Thamnophis sirtalis_). In Kentucky, Barbour (1950:104) recorded remains of an unidentified snake in one stomach.

Many authors likewise have recorded food of the southern black racer (_C. c. priapus_). In Georgia, Wright and Bishop (1915:160) recorded finding 2 racerunners (_Cnemidophorus sexlineatus_), a skink (_Lygosoma laterale_), 4 green tree frogs (_Hyla cinerea_) and 1 pine woods tree frog (_H. femoralis_) in stomachs. They also stated that the toad (_Bufo lentiginosus_ [= _terrestris_]) was the most important article of food. Burt and Hoyle (1934:205) wrote that a racer from Rogers County, Oklahoma, had eaten an adult male collared lizard (_Crotaphytus collaris_). In Florida, Carr (1950:80) found one of these black racers eating a leopard frog (_Rana pipiens_). Hamilton and Pollack (1956:523) examined digestive tracts of 62 and found food in 57, comprising the following percentages by volume: _Lygosoma laterale_, 34.2; _Eumeces fasciatus_ and _E. egregius_, 11.3; _Cnemidophorus sexlineatus_, 8.8; _Sceloporus undulatus_, 3.5; undetermined lizard, 3.5; _Opheodrys aestivus_, 6.6; _Diadophis punctatus_, 3.1; _Storeria dekayi_, 1.6; _Coluber constrictor_, 1.8; _Heterodon platyrhinos_, 1.8; _Masticophis flagellum_, 1.8; _Rana_ sp., 5.3; _Hyla cinerea_, 1.8; _Hyla versicolor_, 1.8; _Peromyscus_, 1.8; undetermined rodent, 1.8; lepidopterous larva, 1.7.

In southern Illinois in an intergrading population of racers intermediate between _C. c. priapus_ and _C. c. flaviventris_, Cagle (1942:188) examined several stomachs and found 1 chipmunk (_Tamias striatus_), 2 voles (_Microtus_ sp.), 2 mice (_Peromyscus_ sp.), 2 green snakes (_Opheodrys_ sp.), 1 water snake (_Natrix sipedon_) and grasshoppers. From this same population Klimstra (1959:212) examined 137 digestive tracts of which 115 contained food as follows: 194 locustids, 118 gryllids, 17 undetermined beetles, 13 carabids, 6 scarabaeids, 10 lepidopterans, 9 hemipterans, 1 hymenopteran, 2 homopterans, 1 dipteran, 17 undetermined insects, 73 _Peromyscus_ sp., 19 _Microtus ochrogaster_, 9 _M. pinetorum_, 12 _Sylvilagus floridanus_, 3 _Scalopus aquaticus_, 3 _Rattus norvegicus_, 4 _Mus musculus_, 2 _Tamias striatus_, 2 _Synaptomys cooperi_, 16 _Rana pipiens_, 8 _Acris crepitans_, 2 _Rana clamitans_, 2 _R. palustris_, 1 _R. catesbeiana_, 4 _Hyla crucifer_, 3 _Pseudacris nigrita_, 4 _Lampropeltis calligaster_, 4 _Sceloporus undulatus_, 4 _Chrysemys picta_, 1 _Heterodon platyrhinos_, 1 unidentified reptile, 4 _Sturnella magna_, 1 _Otocoris alpestris_, 4 unidentified birds. Percentages by volume of the various categories in this sample were: insects, 39.1; mammals, 32.9; amphibians, 10.8; reptiles, 8.3; birds, 6.3; miscellaneous, 2.6.

Food of the "buttermilk snake" (_C. c. anthicus_) is known only through Clark's study (1949:249). In an unstated number of examinations he found "mice" in 25, "rats" in five, lizards (_Sceloporus undulatus_ and perhaps others) in eight, frogs (_Rana pipiens_) in seven, and birds in three.

The food of _C. c. stejnegerianus_ is known only from the work of Auffenberg (1949) but his sample was based on 206 racers that had food, among the total of 291 recorded. Unfortunately, he did not present actual numbers of the various prey animals, but divided the food into seven categories and listed these as percentages. He did not indicate whether the percentages represented volumes or numbers of individual occurrences, and evidently there was some error in computation since his combined percentages totalled 111. The categories and their percentages were as follows: grasshoppers, 42.5; crickets, 13.5; miscellaneous insects, .6; earless lizards (_Holbrookia_ sp.), 40.1; scaly lizards (_Sceloporus_ sp.) 2.1; frogs (_Rana_ sp.) 10.0; rodents, 2.2. Auffenberg divided his sample of racers into five size classes, and showed that the smaller snakes fed chiefly on insects whereas vertebrates were increasingly prominent in the food of the larger snakes.

The food of _C. c. mormon_ is known chiefly through the work of Ortenburger (1928:228) who cited instances of a skink (_Eumeces skiltonianus_) and a young garter snake (_Thamnophis sirtalis_) being eaten, and listed the following items from 24 stomachs that he examined: 7 decticids, 8 acridids, 5 oedipines, 1 tryxaline, 6 _Melanoplus_ sp., 3 _M. mexicanus_, 2 _M. devastator_, 1 _M. bivittatus_, 2 _Dissosteira carolina_, 1 _Chortophaga viridis_, 3 _Neduba carinata_, 3 _Trimerotropus_ sp., 7 _Hippiscus_ sp., 2 _Steiroxys_ sp., 3 _Canoula pellucida_, 2 _Stenopelmatus fuscus_, 2 _S. pictus_, 4 _Gryllus assimilis_, 4 _Ceuthophilus_ sp., 1 _Pristoceuthophilus pacificus_, 6 _Gammarotettix bilobatus_ and 2 cicada nymphs. Grinnell, Dixon and Linsdale (1930:149) found that one of these racers had eaten a cricket. Fitch (1936:644) found another in the act of swallowing an adult vole (_Microtus californicus_), and recorded (1935:18) that two alligator lizards (_Gerrhonotus multicarinatus_) were found in the stomach of still another. Woodbury (1931:75) recorded that a racer from Utah had a sagebrush scaly lizard (_Sceloporus graciosus_) in its stomach. Of the specimens examined in the University of California Museum of Vertebrate Zoology, no. 17256 from the Mad River, Trinity County, California, had eaten an alligator lizard (_Gerrhonotus coeruleus_), and no. 10120 from Yolla Bolly Mountain in the same county had eaten a bird (unidentified) and a Jerusalem cricket (_Stenopelmatus_ sp.).

Several authors have published specific information regarding the food of _C. c. flaviventris_. Hurter (1911:171) caught a blue racer in the act of swallowing a copperhead (_Agkistrodon contortrix_). Taylor (1892:331) recorded finding garter snakes in several large racers. Pope and Dickinson (1928:53) recorded instances of blue racers feeding on racerunners (_Cnemidophorus sexlineatus_). Ortenburger (1928:181) examined 22 stomachs and recorded: 1 large garter snake (_Thamnophis sirtalis_), 1 vole (_Microtus pennsylvanicus_), 1 frog (_Rana_ sp.), 31 crickets (_Gryllus assimilis_), 4 decticines, 2 acridids, grasshoppers (1 _Hippiscus_, 2 _Melanoplus_ sp., 1 _M. confusus_, 1 _M. differentialis_, 1 _Dissosteira carolina_, 1 _Sphargemon collare_, 1 _Trimerotropus_ sp., 1 _Orphulella_ sp., 1 _Chloealtis conspersa_, 1 _Chortophaga viridifasciata_, 1 _Omaseus_ sp., 1 _Pedocetes_ sp.), and 2 caterpillars (1 noctuid, 1 sphingid). Gloyd (1928:123) recorded a hatchling glass lizard (_Ophisaurus attenuatus_) in the stomach of a juvenal racer. Force (1930:31) found a racer eating eggs from the nest of a cardinal (_Richmondena cardinalis_) and another racer eating eggs of a red-wing (_Agelaius phoeniceus_). Gloyd (1932:403) recorded an observation of a racer overpowering and swallowing a copperhead. Anderson (1942:210) recorded remains of crickets and grasshoppers in feces. Hudson (1942:55) recorded a racerunner (_Cnemidophorus sexlineatus_) in the stomach of a juvenile and recorded an earless lizard (_Holbrookia maculata_) 3 lizard eggs, and 14 grasshoppers (_Melanoplus differentialis_ and others) in the stomach of another. Marr (1944:484) found a harvest mouse (_Reithrodontomys montanus_) in one. Breckenridge (1944:118) recorded stomach contents including a garter snake (_Thamnophis sirtalis_), a frog (_Rana pipiens_), 3 crickets and 2 moths. Mossimann and Rabb (1952:27) recorded that a racer disgorged several grasshoppers. Fouquette and Lindsay (1955:411) recorded that a blue racer had eaten a harvest mouse (_Reithrodontomys_ sp.). Carpenter (1958:114) recorded that one blue racer had eaten a green snake (_Opheodrys aestivus_) and another had eaten a grasshopper and a camel cricket.

Even though the sets of data cited above are not entirely comparable, certain trends are evident. The black racers of the eastern states (especially _C. c. constrictor_ of more northern regions) take a high proportion of vertebrates in their prey. Among these vertebrates snakes especially are well represented and the black snake would seem to be of some importance as an ophiphagous predator. The birds and mammals taken include some that are bulky (robin, cottontail, and even a weasel--the most formidable prey eaten). Presumably the rabbits that were eaten were young. In samples from the eastern United States insects made up small to insignificant parts of the food; they were lacking entirely or at least were not mentioned in the samples examined by McCauley and Wright and Bishop. In the blue racer of the central states, insects (mostly grasshoppers and crickets) are much more prominent in the food and vertebrates correspondingly less prominent. The vertebrates eaten are largely lizards, small snakes and mice. _C. c. stejnegerianus_ is much like _flaviventris_ in the trend of its feeding. _C. c. mormon_ is less known than these subspecies in its feeding, but indications are that it takes a higher proportion of orthopteran insects and smaller proportions of mammals and snakes than do any of the other subspecies.

In my own field study a total of 1357 food records were accumulated, one of the largest samples known for any kind of snake. Most of these records were from the small area where my population study was carried on, and studies of other kinds of animals, including those that were the racer's prey, were simultaneously in progress. Because large collections of reference materials were available, it was possible to identify to species many of the prey items found, even though they were incomplete and highly fragmented because most of them were recovered from fecal material.

The prey is, of course, swallowed entire, and the recently swallowed items squeezed from the stomachs provide the best material for the study of food habits. However, relatively few racers had detectable food items in their stomachs; digestion is rapid and often the snake was in a trap for a day or more before it was found. Therefore the greater number of records were obtained from scats. The residue in scats consisted entirely of hard and indigestible parts such as the chitin of insects' exoskeletons and the hair, feathers, scales, teeth and occasional bone fragments of the vertebrate prey. The insects eaten could usually be counted individually by sorting parts, such as heads or hind legs. With mammals, birds and reptiles the hair, feathers, or scales did not permit counting of individuals--each occurrence was assumed to represent one individual but in some instances two or more may have been present. Amphibians, lacking indigestible dermal structures were in most instances not represented at all in the scats, since their tissues were more or less completely dissolved by the digestion of the snakes. Soft-bodied larvae of insects and other invertebrates conceivably could be likewise completely digested, but such occurrences must be rare, as most of the invertebrates known to be eaten have the mouth parts, at least, heavily chitinized.

Admittedly the factors discussed above would cause some bias in the percentage composition of the food determined from scats, but I believe that the amount of error introduced was slight, because, judging from the records of items from stomachs, amphibians are not eaten frequently, and even mammals are not eaten frequently enough so that there is much chance of a snake taking two or more individuals at the same meal, unless it is robbing a nest containing a litter of young.

The largest sample, based on 1008 food items, was obtained from 479 scats collected from the Reservation and Rockefeller Tract over the period 1949 through 1961. Items recorded were: 183 gryllid crickets (144 _Gryllus assimilis_, 36 _Gryllus_ sp., 3 unspecified); 353 locustid grasshoppers (41 unspecified, 73 _Arphia simplex_, 67 _Melanoplus femur-rubrum_, 66 _M. bivittatus_, 39 _M. differentialis_, 17 _Melanoplus_ sp., 15 _Dissosteira carolina_, 8 _Chortophaga viridifasciata_, 6 _Syrbula admirabilis_, 6 _Sphargemon equale_, 2 _Melanoplus scudderi_, 2 _Schistocerca obscura_, 1 _S. americana_); 94 camel crickets (_Ceuthophilus_ sp.), 93 katydids (36 _Neoconocephalus robustus_, 15 _Orchelimum vulgare_, 15 _O. nigripes_, 6 _Conocephalus_ sp., 4 _Orchelimum_ sp., 2 _Amblycorypha inasteca_, 1 _Neoconocephalus_ sp., 1 _Daihinia brevipes_); 7 cicadas (5 _Tibicen_ sp., 1 _T. pruinosa_, 1 _T. lyrica_); 45 unidentified insects; 17 beetles (including 1 _Phyllophaga_, 1 _Calosoma scrutator_, and 2 other carabids); 2 noctuid moths (_Mocis latipes_) and 1 caterpillar; 2 homopterans, 1 bee, 1 ant, 1 spider; 69 voles (59 _Microtus ochrogaster_, 9 _Microtus_ sp., 1 _M. pinetorum_); 31 white-footed mice (15 _Peromyscus leucopus_, 14 _Peromyscus_ sp., 1 _P. maniculatus_); 36 miscellaneous small mammals (6 _Cryptotis parva_, 4 _Sigmodon hispidus_, 4 _Reithrodontomys megalotis_, 3 _Blarina brevicauda_, 2 each of _Scalopus aquaticus_, _Sylvilagus floridanus_, and 1 unspecified shrew); 50 snakes (16 _Coluber constrictor_, 15 _Diadophis punctatus_, 14 _Thamnophis sirtalis_, 4 _Elaphe obsoleta_, 1 _Natrix sipedon_); 7 lizards (5 _Eumeces fasciatus_, 1 _E._ _obsoletus_, 1 _Cnemidophorus sexlineatus_); 3 unspecified "reptiles"; 5 birds (none identified to genus); 3 bird eggs, 1 narrow-mouthed toad (_Gastrophryne olivacea_).

Over the same period that the sample of scats was collected, a much smaller food sample of 73 prey items was collected by squeezing recently eaten food from the racers' stomachs, or by finding the snakes actually swallowing their prey. These items from stomachs are listed separately because they include relatively more vertebrates than do the items from scats. A grasshopper or cricket eaten by a large racer might have passed undetected, while a relatively large item such as a vole or lizard would have produced a conspicuous bulge in the snake that ate it, and would have excited the curiosity of the investigator. A second difference is that the items from stomachs included several frogs, whereas amphibians were absent from the much larger sample from scats. A third difference is that the many insects found in stomachs were all orthopterans with the exceptions of three noctuid moths and the larva of a moth. Miscellaneous insects, such as beetles, bees and ants recorded from scats were not found in stomachs. Amphibians eaten are digested so completely that no recognizable parts of them are to be found in scats, but remains of the insects previously eaten by amphibians are to be seen in racers' scats. If not recognized as secondary items, such remains might lead to erroneous conclusions regarding the racer's food.

The items from stomachs were as follows: 21 grasshoppers (5 oedipines, 4 tryxalines, 5 _Melanoplus bivittatus_, 3 _M. differentialis_, 1 _M. femur-rubrum_ and one each of _Chortophaga viridifasciata_, _Dissosteira carolina_, and _Sphargemon equale_); 8 crickets (_Gryllus_ sp.), 3 katydids, 3 camel crickets (_Ceuthophilus_ sp.), 3 noctuid moths, 1 larva of a moth; 10 voles (_Microtus ochrogaster_), 6 white-footed mice (5 _Peromyscus leucopus_ and 1 _P. maniculatus_), 4 harvest mice (_Reithrodontomys megalotis_); 1 shrew (_Cryptotis parva_); 4 snakes (3 _Thamnophis sirtalis_, 1 _Storeria dekayi_); 4 lizards (2 _Eumeces obsoletus_, 1 _Cnemidophorus sexlineatus_, 1 _Ophisaurus attenuatus_); 4 frogs (_Rana pipiens_), 1 tree-frog (_Hyla versicolor_).

Records from the Harvey County, Kansas study area include a series of 69 food items from 55 stomachs (of living snakes) and 210 food items from 113 scats. There is a relatively high proportion of vertebrates, including some frogs, in the stomachs, and with no frogs but more miscellaneous insect material in the scats. But, for the sake of brevity, the two categories of items are combined in the following list: 55 grasshoppers (12 unspecified, 1 "locustid," 31 "oedipines," 7 "tryxalines," 5 "locustines," 2 _Melanoplus bivittatus_ and one each of _M. femur-rubrum_, _M. scudderi_, _M. differentialis_, and _Arphia simplex_); 48 crickets (31 _Gryllus assimilis_, 17 unspecified); 14 katydids (11 _Daihinia brevipes_, one each of rhadiphorine, conocephaline and _Neoconocephalus_ sp.); 9 noctuid moths and 1 moth larva; 26 miscellaneous insects (including 13 "beetles," 1 elaterid, 1 curculionid, 1 lygaeid bug, 1 ant, 1 wasp); 1 spider, 7 mice (5 _Peromyscus maniculatus_, 2 unspecified), 4 unidentified mammals, 1 vole (_Microtus ochrogaster_), 1 shrew (_Cryptotis parva_), 84 lizards (77 _Cnemidophorus sexlineatus_, 6 _Sceloporus undulatus_, 1 unspecified), 6 snakes (4 "natricines," 1 _Thamnophis_ sp., 1 _Pituophis melanoleucus_), 1 "reptile," 1 "bird," 9 frogs (4 unspecified, 1 _Rana catesbeiana_, 4 _Rana pipiens_, 1 _Rana_ sp., 1 _Pseudacris triseriata_).

_Kinds of Prey_

Throughout the range of the racer small mammals make up an important portion of the food, and the bulk of those eaten are voles (_Microtus_ sp.) and white-footed mice (_Peromyscus_ sp.). The voles being diurnal, and having habitat preferences similar to those of the racer, are especially subject to attack, but only large adult racers are capable of swallowing a full grown vole. Probably most of the voles eaten are immature. Of the white-footed mice, _P. maniculatus_ especially prefers a grassland habitat, and is usually found in situations frequented by the racer. Being mainly nocturnal and crepuscular, it is usually in hiding at times when the racer is prowling, but may be flushed from its nest in a shallow burrow or beneath a sheltering object, and overtaken by the snake. Other mammals that are important in the food are harvest mice and other mice, shrews, and young cottontails. The latter are small enough to be eaten by racers only in the early stages of their life in the nest before weaning. Rats (_Rattus_, _Sigmodon_), moles, sciurids, and weasels are less frequent prey, ordinarily too large to be eaten by racers and taken chiefly as defenseless juveniles.

Predation on birds is relatively uncommon, and in most instances it involves the eggs or nestlings, or fledglings still slow and clumsy and incapable of sustained flight, or, occasionally, injured adults. Nests that are vulnerable are chiefly those of ground nesting species, or of kinds that nest near the ground in grass or thickets. Many of the birds recorded have not been identified to species, but those identified have included a variety of small passerines and also domestic chicks.