Chapter I: Part 1

Transcriber's Note

Italic text is presented as _Text_.

UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY

Volume 18, No. 5, pp. 421-504

August 20, 1969

Comparative Ecology of Pinyon Mice
and Deer Mice in
Mesa Verde National Park, Colorado

BY
CHARLES L. DOUGLAS

UNIVERSITY OF KANSAS
LAWRENCE
1969

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors of this number: Frank B. Cross, Philip S. Humphrey,
J. Knox Jones, Jr.

Volume 18, No. 5, pp. 421-504
Published August 20, 1969

UNIVERSITY OF KANSAS
Lawrence, Kansas

PRINTED BY
ROBERT R. (BOB) SANDERS, STATE PRINTER
TOPEKA, KANSAS
1969

32-6879

CONTENTS

PAGE

INTRODUCTION 424
Physiography 425
Vegetation and Climate 427

ACKNOWLEDGMENTS 427

DESCRIPTIONS OF MAJOR TRAPPING LOCALITIES 428

HOME RANGE 435
Calculations of Home Range 437
Analysis by Inclusive Boundary Strip 439
Analysis by Exclusive Boundary Strip 440
Adjusted Length of Home Range 440
Distance Between Captures 441

VEGETATIONAL ANALYSIS OF HABITATS 446

MICROCLIMATES OF DIFFERENT HABITATS 450

HABITAT PREFERENCE 459

NESTING AND NEST CONSTRUCTION 461

REPRODUCTION 465

GROWTH 469

PARENTAL BEHAVIOR 471
Transportation of Young 472

CHANGES OWING TO INCREASE IN AGE 475

ANOMALIES AND INJURIES 476
Losses Attributed to Exposure in Traps 477
Dental Anomalies 478
Anomalies in the Skull 478

FOOD HABITS 479

WATER CONSUMPTION 482

PARASITISM 491

PREDATION 493

DISCUSSION 495
Factors Affecting Population Densities 497
Adaptations to Environment 499

LITERATURE CITED 501

INTRODUCTION

Centuries ago in southwestern Colorado the prehistoric Pueblo inhabitants of the Mesa Verde region expressed their interest in mammals by painting silhouettes of them on pottery and on the walls of kivas. Pottery occasionally was made in the stylized form of animals such as the mountain sheep. The silhouettes of sheep and deer persist as pictographs or petroglyphs on walls of kivas and on rocks near prehistoric dwellings. Mammalian bones from archeological sites reveal that the fauna of Mesa Verde was much the same in A. D. 1200, when the Pueblo Indians were building their magnificent cliff dwellings, as it is today. One of the native mammals is the ubiquitous deer mouse, _Peromyscus maniculatus_. The geographic range of this species includes most of the United States, and large parts of Mexico and Canada.

Another species of the same genus, the pinyon mouse, _P. truei_, also lives on the Mesa Verde. The pinyon mouse lives mostly in southwestern North America, occurring from central Oregon and southern Wyoming to northern Oaxaca. This species generally is associated with pinyon pine trees, or with juniper trees, and where the pinyon-juniper woodland is associated with rocky ground (Hoffmeister, 1951:vii).

_P. maniculatus rufinus_ of Mesa Verde was considered to be a mountain subspecies by Osgood (1909:73). The center of dispersion for _P. truei_ was in the southwestern United States, and particularly in the Colorado Plateau area (Hoffmeister, 1951:vii). The subspecies _P. truei truei_ occurs mainly in the Upper Sonoran life-zone, and according to Hoffmeister (1951:30) rarely enters the Lower Sonoran or Transition life-zones. _P. maniculatus_ and _P. truei_ are the most abundant of the small mammals in Mesa Verde National Park, which comprises about one-third of the Mesa Verde land mass.

Under the auspices of the Wetherill Mesa Archeological Project, the flora of the park recently was studied by Erdman (1962), and by Welsh and Erdman (1964). These studies have revealed stands of several distinct types of vegetation in the park and where each type occurs. This information greatly facilitated my study of the mammals inhabiting each type of association. The flora and fauna within the park are protected, in keeping with the policies of the National Park Service, and mammals, therefore, could be studied in a relatively undisturbed setting.

Thus, the abundance of these two species of _Peromyscus_, the botanical studies that preceded and accompanied my study, the relatively undisturbed nature of the park, and the availability of a large area in which extended studies could be carried on, all contributed to the desirability of Mesa Verde as a study area.

My primary purpose in undertaking a study of the two species of _Peromyscus_ was to analyze a number of ecological factors influencing each species--their habitat preferences, how the mice lived within their habitats, what they ate, where they nested, what preyed on them, and how one species influenced the distribution of the other. In general, my interest was in how the lives of the two species impinge upon each other in Mesa Verde.

Physiography

The Mesa Verde consists of about 200 square miles of plateau country in southwestern Colorado, just northeast of Four Corners, where Colorado, New Mexico, Arizona and Utah meet. In 1906, more than 51,000 acres of the Mesa Verde were set aside, as Mesa Verde National Park, in order to protect the cliff dwellings for which the area is famous.

The Mesa Verde land mass is composed of cross-bedded sandstone strata laid down by Upper Cretaceous seas. These strata are known locally as the Mesaverde group, and are composed, from top to bottom, of Cliff House sandstone, the Menefee formation, the Point Lookout sandstone, the well known Mancos shale, and the Dakota sandstone, the lowest member of the Cretaceous strata. The Menefee formation is 340 to 800 feet thick, and contains carbonaceous shale and beds of coal.

There are surface deposits of Pleistocene and Recent age, with gravel and boulders of alluvial origin; colluvium composed of heterogeneous rock detritus such as talus and landslide material; and alluvium composed of soil, sand, and gravel. A layer of loess overlays the bedrock of the flat mesa tops in the Four Corners area. The earliest preserved loess is probably pre-Wisconsin, possibly Sangamon in age (Arrhenius and Bonatti, 1965:99).

The North Rim of Mesa Verde rises majestically, 1,500 feet above the surrounding Montezuma Valley. Elevations in the park range from 8,500 feet at Park Point to about 6,500 feet at the southern ends of the mesas. The Mesa Verde land mass is the remnant of a plateau that erosion has dissected into a series of long, narrow mesas, joined at their northern ends, but otherwise separated by deep canyons. The bottoms of these canyons are from 600 to 900 feet below the tops of the mesas.

The entire Mesa Verde land mass tilts southward; Park Headquarters, in the middle of Chapin Mesa (Fig. 1), is at about the same elevation as is the entrance of the park, 20 miles by road to the north.

Vegetation and Climate

Mesa Verde is characterized by pinyon-juniper woodlands that extend throughout much of the West and Southwest. Although the pinyon-juniper woodland dominates the mesa tops, stands of Douglas fir occur in some sheltered canyons and on north-facing slopes. Thickets of Gambel oak and Utah serviceberry cover many hillsides and form a zone of brush at higher elevations in the park. Aspens grow in small groups at the base of the Point Lookout sandstone and at a few other sheltered places where the supply of moisture suffices. Individual ponderosa pine are scattered through the park, and stands of this species occur on some slopes and in the bottoms of some sheltered canyons.

Tall sagebrush grows in deep soils of canyon bottoms, and in some burned areas, and was found to be a good indicator of prehistoric occupation sites.

The climate of Mesa Verde is semi-arid, and most months are dry and pleasant. Annual precipitation has averaged about 18.5 inches for the last 40 years. July and August are the months having the most rainfall. Snow falls intermittently in winter, and may persist all winter on north-facing slopes and in valleys. In most years, snow is melting and the kinds of animals that hibernate are emerging by the first of April.

Because of the great differences in elevation between the northern and southern ends of the mesas, differences in climate are appreciable at these locations. Winter always is the more severe on the northern end of the park, owing to persistent winds, lower temperatures, and more snow. The northern end of the park is closer to the nearby La Platta Mountains where ephemeral storms of summer originate. They reach the higher elevations of the park first, but such storms dissipate rapidly and are highly localized. The northern end of the park therefore receives much more precipitation in summer and winter than does the southern end.

The difference in precipitation and the extremes in weather between the northern and southern ends of the mesas affect the distribution of plants and animals. Species of mammals, plants, and reptiles are most numerous on the middle parts of the mesas, as also are cliff-dwellings, surface sites, and farming terraces of the prehistoric Indians.

Anderson (1961) reported on the mammals of Mesa Verde National Park, and Douglas (1966) reported on the amphibians and reptiles. In each of these reports, earlier collections are listed and earlier reports are summarized.

I lived in Mesa Verde National Park for 28 months in the period July 1961 to September 1964, while working as Biologist for the Wetherill Mesa Archeological Project, and the study here reported on is one of the faunal studies that I undertook.

ACKNOWLEDGMENTS

This study could not have been completed without the assistance and encouragement of numerous persons. I am grateful to Dr. Olwen Williams, of the University of Colorado, for suggesting this study and helping me plan the early phases of it.

Mr. Chester A. Thomas, formerly Superintendent, and Mrs. Jean Pinkley, formerly Chief of Interpretation at Mesa Verde National Park, permitted me to use the park's facilities for research, issued collecting permits, and in 1965 appointed me as a research collaborator in order that I might complete my studies.

Dr. H. Douglas Osborne, California State College, Long Beach, formerly Supervisory Archeologist of the Wetherill Mesa Project, took an active interest in my research and provided supplies, transportation and laboratory and field assistance under the auspices of the Wetherill Project. His assistance and encouragement are gratefully acknowledged.

Mrs. Marilyn A. Colyer of Mancos, Colorado, ably assisted in analyzing vegetation in the trapping grid; Mr. Robert R. Patterson, the University of Kansas, assisted me in the field in October of 1963 and in August of 1965. Mr. James A. Erdman, United States Geological Survey, Denver, formerly Botanist for the Wetherill Mesa Project, and Dr. Stanley L. Welsh, Brigham Young University, identified plants for me in the field, and checked my identifications of herbarium specimens. I owe my knowledge of the flora in the park to my association with these two capable botanists.

I am grateful to the following persons for identification of invertebrates: D. Eldon Beck, fleas and ticks; Paul Winston, mites; V. Eugene Nelson, mites; William Wrenn, mites; Wayne W. Moss, mites; William B. Nutting, mites (_Desmodex_); Marilyn A. Colyer, insects; John E. Ubelaker, endoparasites; Veryl F. Keen, botflies. George A. King, Architect, of Durango, Colorado, prepared the original map for Figure 1.

Mr. Harold Shepherd of Mancos, Colorado, Senior Game Biologist, Colorado Department of Fish, Game and Parks, obtained permission for me to use the department's trapping grid near Far View Ruins, and provided me with preserved specimens of mice.

Mr. Fred E. Mang Jr., Photographer, National Park Service, processed large numbers of photomicrographs of plant epidermis. Dr. Kenneth B. Armitage, The University of Kansas, offered valuable suggestions for the study of water consumption in the two species of _Peromyscus_, and permitted me to use facilities of the Zoological Research Laboratories at The University of Kansas. Dr. Richard F. Johnston, The University of Kansas, permitted me to house mice in his controlled-temperature room at the Zoological Research Laboratories. I am grateful to all of the above mentioned persons for their aid.

I acknowledge with gratitude the guidance, encouragement, and critical assistance of Professor E. Raymond Hall throughout the course of the study and preparation of the manuscript. I also extend my sincere thanks to Professors Henry S. Fitch, Robert W. Baxter, and William A. Clemens for their helpful suggestions and assistance.

To my wife, Virginia, I am grateful for encouragement and assistance with many time-consuming tasks connected with field work and preparation of the manuscript.

Travel funds provided by the Kansas Academy of Science permitted me to work in the park in August, 1965. The Wetherill Mesa Project was an interdisciplinary program of the National Park Service to which the National Geographic Society contributed generously. I am indebted to the Society for a major share of the support that resulted in this report. This is contribution No. 44 of the Wetherill Mesa Project.

DESCRIPTIONS OF MAJOR TRAPPING LOCALITIES

Trapping was begun in September of 1961 in order to analyze the composition of rodent populations within the park. I used the method of trapping employed by Calhoun (1948) in making the Census of North American Small Mammals (N. A. C. S. M.). It consisted of two lines of traps, each 1,000 feet long having 20 trapping stations that were 50 feet apart. The lines were either parallel at a distance of 400 feet from each other, or were joined to form a line 2,000 feet long. Three snap traps were placed within a five-foot radius of each station, and were set for three consecutive nights. More than a dozen areas were selected for extensive trapping (Fig. 1). Some of these were retrapped in consecutive years in order to measure changes in populations.

One circular trapline of 159.5 feet radius was established in November 1961, and was tended for 30 consecutive days to observe the effect of removing the more dominant species (Calhoun, 1959).

Other mouse traps and rat traps were set in suitable places on talus slopes, rocky cliffs, and in cliff dwellings. Most of these traps were operated for three consecutive nights.

In order to test hypotheses concerning habitat preferences of each of the species of _Peromyscus_, several previously untrapped areas that appeared to be ideal habitat for one species, but not for the other, were selected for sampling. In the summers of 1963 and 1964 snap traps were set along an arbitrary line through each of these areas. Traps were placed in pairs; each pair was 20 feet from the adjacent pairs.

A mixture of equal parts of peanut butter, bacon grease, raisins, roman meal and rolled oats was used as bait. Rolled oats or coarsely ground scratch feed was used in areas where insects removed the mixture from the traps.

Rodents trapped by me were variously prepared as study skins with skulls, as flat skins with skulls, as skeletons, as skulls only, or as alcoholics. Representative specimens were deposited in The University of Kansas Museum of Natural History. In the course of my study, traps were set in the following areas:

_Morfield Ridge_

In July 1959 a fire destroyed more than 2,000 acres of pinyon-juniper forest (_Pinus edulis_ and _Juniperus osteosperma_) in the eastern part of the park. The burned area extends from Morfield Canyon to Waters Canyon, encompassing several canyons, Whites Mesa, and a ridge between Morfield Canyon and Waters Canyon that is known locally as Morfield Ridge (Fig. 1). Beginning on September 4, 1961, three pairs of traplines were run on this ridge at elevations of 7,300 to 7,600 feet.

Vegetation in the trapping area consisted of dense growths of grasses and herbaceous plants, which had covered the ground with seeds. In this and in the following accounts, the generic and specific names of plants are those used by Welsh and Erdman (1964). The following plants were identified from the trapping area on Morfield Ridge:

_Lithospermum ruderale_
_Chenopodium pratericola_
_Achillea millefolium_
_Artemisia tridentata_
_Aster bigelovii_
_Chrysothamnus depressus_
_Chrysothamnus nauseosus_
_Helianthus annuus_
_Helianthella_ sp.
_Lactuca_ sp.
_Lepidium montanum_
_Quercus gambelii_
_Agropyron smithii_
_Bromus inermis_
_Bromus japonicus_
_Oryzopsis hymenoides_
_Calochortus nuttallii_
_Linum perenne_
_Sphaeralcea coccinea_
_Polygonum sawatchense_
_Solidago petradoria_
_Wyethia arizonica_
_Nicotiana attenuata_
_Fendlera rupicola_
_Penstemon linarioides_

Only _Peromyscus maniculatus_, _Perognathus apache_ and _Reithrodontomys megalotis_ were taken in this area (Table 1). Many birds inhabit this area, including hawks, ravens, towhees, jays, juncos, woodpeckers, doves, sparrows and titmice. Rabbits, badgers and mule deer also live in the area. Only two reptiles, a horned lizard and a collared lizard, were seen.

_South of Far View Ruins_

Two parallel trap lines were established on October 4, 1961, in the area immediately south of Far View Ruins (Fig. 1). In altitude, latitude and geographical configuration the area is similar to that trapped in the Morfield burn, but the Chapin Mesa site had not been burned.

Canopy vegetation is pinyon-juniper forest. A dense understory was made up of _Amelanchier utahensis_ (serviceberry), _Cercocarpos montanus_ (mountain mahogany), _Purshia tridentata_ (bitterbrush), and _Quercus gambelii_ (Gambel oak). The ground cover consisted of small clumps of _Poa fendleriana_ (muttongrass), and _Koeleria cristata_ (Junegrass), intermingled with growths of one or more of the following:

_Artemisia nova_
_Solidago petradoria_
_Sitanion hystrix_
_Astragalus scopulorum_
_Lupinus caudatus_
_Eriogonum alatum_
_Penstemon linarioides_
_Eriogonum racemosum_
_Eriogonum umbellatum_
_Polygonum sawatchense_
_Amelanchier utahensis_
_Purshia tridentata_
_Comandra umbellata_

Seeds of _Cercocarpos montanus_ covered the ground under the bushes in much of the trapping area, and large numbers of juniper berries were on the ground beneath the trees. Individuals of _P. truei_ and _P. maniculatus_ were caught in this area (Table 1).

Several deer, rabbits, one coyote, and numerous birds were seen in the area. No reptiles were noticed, but they were not searched for. A mountain lion was seen in this general area two weeks after trapping was completed.

_West of Far View Ruins_

Three pairs of traplines were run west of Far View Ruins in an area comparable in vegetation, altitude, general topography, and configuration to the area previously described. The elevations concerned are typical of the middle parts of mesas throughout the park. This area differs from the trapping area south of Far View Ruins and the one on Morfield Ridge in being wider and on the western side of the mesa.

The woody understory was sparse in most places, and where present was composed of _Cercocarpos montanus_, _Purshia tridentata_, _Fendlera rupicola_ (fendlerbush), _Amelanchier utahensis_, _Quercus gambelii_, and _Artemisia tridentata_ (sagebrush). The herbaceous ground cover was dominated by _Solidago petradoria_ (rock goldenrod), and grasses--including _Poa fendleriana_, _Oryzopsis hymenoides_, and _Sitanion hystrix_. Other herbaceous species were as follows:

_Echinocercus coccineus_
_Achillea millefolium_
_Aster bigelovii_
_Wyethia arizonica_
_Lepidium montanum_
_Lupinus caudatus_
_Yucca baccata_
_Linum perenne_
_Eriogonum racemosum_
_Eriogonum umbellatum_
_Polygonum sawatchense_
_Delphinium nelsonii_
_Penstemon linarioides_

Fresh diggings of pocket gophers were observed along the trap lines. Badger tunnels were noted in numerous surface mounds that are remnants of prehistoric Indian dwellings, but no badgers were seen. Numerous deer and several rabbits were present. Juncos, two species of jays, and woodpeckers were seen daily. No reptiles were observed.

Both _Peromyscus maniculatus_ and _P. truei_ were caught in this area (Table 1).

_Big Sagebrush Stand, South Chapin Mesa_

A circular trapline, 1,000 feet in circumference, was established on November 16, 1961, in a stand of big sagebrush, and was operated for 30 consecutive nights.

The vegetation of the trapping area was predominantly _Artemisia tridentata_ (big sagebrush), interspersed with a few scattered seedlings of pinyon and juniper. This stand was burned in 1858 (tree-ring date by David Smith) and some charred juniper snags still stood. The deep sandy soil also supported a variety of grasses and a few other small plants. The following species were common in this area:

_Bromus inermis_
_Oryzopsis hymenoides_
_Poa fendleriana_
_Sitanion hystrix_
_Solidago petradoria_
_Orthocarpus purpureo-albus_

The 15 to 20 acres of sagebrush were surrounded by pinyon-juniper forest. The trapping station closest to the forest was approximately 100 feet from the edge of the woodland. More _P. truei_ than _P. maniculatus_ were caught here (Table 1).

_East Loop Road, Chapin Mesa_

The trapping area lies north of Cliff Palace, eastward of the loop road, at elevations of 6,875 to 6,925 feet. Two pairs of traplines were run from January 9, 1962, to January 12, 1962, and from February 13 to 15, 1962.

Vegetation was pinyon-juniper woodland with an understory of mixed shrubs. One to four inches of old snow covered the ground during most of the trapping period, but the ground beneath trees and shrubs was generally clear, providing suitable location for traps.

Numerous juncos and jays were seen in this area; deer and rabbits also were present.

Individuals of _P. truei_ and of _P. maniculatus_ were taken (Table 1).

_Navajo Hill, Chapin Mesa_

Navajo Hill is the highest point (8,140 feet) on Chapin Mesa. The top of the hill is rounded and the sides slope gently southward and westward until they level out into mesa-top terrain at elevations of 7,950 to 8,000 feet. The northern and eastern slopes of the hill drop abruptly into the respective canyon slopes of the East Fork of Navajo Canyon and the West Fork of Little Soda Canyon. The gradually tapering southwestern slope of the hill extends southward for one mile and is bisected by the main highway, which runs the length of the mesa top.

Heavy growths of grasses cover the ground; _Amelanchier utahensis_, _Cercocarpos montanus_, and _Fendlera rupicola_ comprise the only tall vegetation. Trees are lacking on this part of the mesa, except on the canyon slopes, where _Quercus gambelii_ forms an almost impenetrable barrier.

Four traplines were run from May 4-7, 1962, and from May 9-12, 1962. _P. maniculatus_ was taken but _P. truei_ was not present here in 1962, or in 1964 or 1965 when additional trapping was performed as a check on populations (Table 1).

Other species trapped include the montane vole, long-tailed vole, and Colorado chipmunk. Mule deer and coyotes were abundant in the area. Striped whipsnakes, rattlesnakes and gopher snakes are known to occur in this vicinity (Douglas, 1966).

_North End Wetherill Mesa_

In 1934 a widespread fire deforested large areas of pinyon-juniper woodland on the northern end of Wetherill Mesa. The current vegetation consists of shrubs with a dense ground cover of grasses. Many dead trees still remain on the ground, providing additional cover for wildlife.

The trapping area was a wide, grassy meadow, three and a half miles south of the northern end of the mesa. A pronounced drainage runs through this area and empties into Rock Canyon. Four traplines were run parallel to each other. The first lines were established on May 23, 1962, and the second pair on June 3, 1962.

Another pair of lines was run in a grassy area two miles south of the northern escarpment of Wetherill Mesa. This area was one and a half miles north of the above-mentioned area. These lines ran along the eastern side of a drainage leading into Long Canyon. The vegetation was essentially the same in both areas, and they will be considered together.

The vegetation was composed predominantly of grasses. _Quercus gambelii_ and _Amelanchier utahensis_ were the codominant shrubs. _Artemisia tridentata_ and _Chrysothamnus depressus_ (dwarf rabbitbrush), were common. Plants in the two areas included the following:

_Juniperus scopulorum_
_Symphoricarpos oreophilus_
_Artemisia ludoviciana_
_Sitanion hystrix_
_Stipa comata_
_Astragalus scopulorum_
_Artemisia tridentata_
_Chrysothamnus depressus_
_Helianthus annuus_
_Tetradymia canescens_
_Quercus gambelii_
_Bromus tectorum_
_Poa fendleriana_
_Lupinus caudatus_
_Yucca baccata_
_Sphaeralcea coccinea_
_Eriogonum umbellatum_
_Amelanchier utahensis_
_Fendlera rupicola_
_Lomatium pinatasectum_

Individuals of _P. maniculatus_ and of _Reithrodontomys megalotis_ were caught (Table 1).

TABLE 1--Major Trapping Localities in Mesa Verde National Park,
Colorado.

Vegetational Key as Follows: 1) Pinyon-Juniper-Muttongrass
2) Pinyon-Juniper-Mixed Shrubs 3) Juniper-Pinyon-Bitterbrush
4) Juniper-Pinyon-Mountain Mahogany 5) Grassland with Mixed Shrubs
6) Big Sagebrush 7) Pinyon-Juniper-Big Sagebrush 8) Grassland.

Column headings:

A: Date
B: No. trap nights
C: _P. truei_
D: _P. man._
E: Type of vegetation

========================+=============+=======+=====+=====+===
Locality | A | B | C | D | E
------------------------+-------------+-------+-----+-----+---
Morfield Ridge | Sept. 1961 | 1080 | 0 | 83 | 5
| Oct. 1963 | 360 | 0 | 13 | 5
| | | | |
S. of Far View | Oct. 1961 | 360 | 10 | 13 | 2
| | | | |
W. of Far View | Oct. 1961 | 1080 | 22 | 17 | 2
| | | | |
South Chapin Mesa | Nov.-Dec. | 3600 | 16 | 9 | 6
| 1961 | | | |
| | | | |
East Loop Road | Jan. 1962 | 720 | 6 | 2 | 2
| | | | |
Navajo Hill | May 1962 | 720 | 0 | 18 | 5
| Aug. 1964 | 20 | 0 | 2 | 5
| Aug. 1965 | 50 | 0 | 8 | 5
| | | | |
N. Wetherill Mesa | May-June | 1080 | 0 | 57 | 5
| 1962 | | | |
| | | | |
Bobcat Canyon Drainage | June 1962 | 360 | 0 | 0 | 6
| | | | |
N. of Long House | June 1962 | 1080 | 3 | 4 | 1
| | | | |
Mug House--Rock Springs | Aug. 1962 | 720 | 8 | 14 | 4
| Aug. 1963 | 720 | 9 | 7 | 4
| | | | |
S. Wetherill Mesa | Aug. 1962 | 720 | 0 | 5 | 3
| | | | |
1 mi. SE Park Entr. | June 1963 | 50 | 0 | 16 | 7
| | | | |
1/4 mi. SE Park Entr. | July 1963 | 100 | 0 | 7 | 8
| | | | |
M-2 Weather Sta. | May 1964 | 25 | 2 | 0 | 1
| | | | |
8 mi. S North Rim | | | | |
Moccasin Mesa | Aug. 1964 | 100 | 0 | 3 | 8
| | | | |
10 mi. S North Rim | | | | |
Moccasin Mesa | Aug. 1964 | 25 | 2 | 0 | 2
------------------------+-------------+-------+-----+-----+---

_Bobcat Canyon Drainage_

Bobcat Canyon, a large secondary canyon on the eastern side of Wetherill Mesa, is a major drainage for much of the mesa at its widest part. The mesa top drains southeast into a pour-off at the head of Bobcat Canyon. A stand of big sagebrush, _Artemisia tridentata_, grows in the sandy soil of the drainage, and extends northwest for several hundred yards from the pour-off. The sagebrush invades the pinyon-juniper forest at the periphery of the area.

Two traplines were set in the drainage, with trapping stations at intervals of 25 feet. The lines traversed elevations of 7,000 to 7,100 feet, and were run from June 26 to 29, 1962.

Grasses are the most abundant plants in the ground cover. _Artemisia dracunculus_ is common in the drainage, and _A. nova_ grows around the periphery of the drainage. Other species occurring in this stand include:

_Aster bigelovii_
_Tetradymia canescens_
_Tragopogon pratensis_
_Bromus tectorum_
_Poa fendleriana_
_Sitanion hystrix_
_Stipa comata_
_Lupinus argenteus_
_Calochortus gunnisonii_
_Sphaeralcea coccinea_
_Phlox hoodii_
_Eriogonum umbellatum_
_Peraphyllum ramosissimum_
_Purshia tridentata_
_Penstemon linarioides_

No mice were caught in three nights of trapping (360 trap nights), and only one mammal, a _Spermophilus variegatus_, was seen.

_North of Long House, Wetherill Mesa_

Pinyon-juniper forest with a dominant ground cover of _Poa fendleriana_ was described by Erdman (1962) as one of the three distinct types of pinyon-juniper woodland on Wetherill Mesa. Such a woodland occurs adjacent to the Bobcat Canyon drainage, and is continuous across the Mesa from above Long House to the area near Step House. Plants in the ground cover include:

_Cryptantha bakeri_
_Opuntia rhodantha_
_Chrysothamnus depressus_
_Solidago petradoria_
_Koeleria cristata_
_Lupinus argenteus_
_Yucca baccata_
_Phlox hoodii_
_Eriogonum racemosum_
_Eriogonum umbellatum_
_Cordylanthus wrightii_
_Pedicularis centranthera_
_Penstemon linarioides_
_Penstemon strictus_

Two traplines were run from July 9 to 12, 1962, in the area south of the Bobcat Canyon drainage at an elevation of 7,100 feet. No mice were caught in three nights of trapping. Four additional lines were established on July 24, 1962, and were run for three nights, in the area north of the Bobcat Canyon drainage at elevations of 7,100 to 7,150 feet.

_P. maniculatus_ and _P. truei_ were caught here (Table 1). This vegetational association may have few rodents because there is a shortage of places where they can hide. Although _Poa fendleriana_ is abundant, the lack of shrubs leaves little protective cover for mammals.

_Mug House--Rock Springs_

A juniper-pinyon-mountain mahogany association extends from the area of Mug House to Rock Springs, on Wetherill Mesa. On that part of the ridge just above Mug House, the understory is predominantly _Cercocarpos montanus_ (mountain mahogany), but northward toward Rock Springs the understory changes to _Fendlera rupicola_, _Amelanchier utahensis_, _Cercocarpos_, and _Purshia tridentata_. The ground cover is essentially the same as that in the pinyon-juniper-muttongrass association described previously.

Four traplines were run from July 31 to August 2, 1962, and from August 13 to 15, 1963. These lines ran northwest-southeast, starting 1,000 feet southeast of, and ending 3,000 feet northwest of, Mug House. The lines traversed elevations of 7,225 to 7,325 feet. Individuals of _P. maniculatus_ and _P. truei_ were caught here (Table 1).

Deer and rabbits inhabit the trapping area. Bobcats have been seen, by myself and by others, near Rock Springs. Lizards of the genera _Cnemidophorus_ and _Sceloporus_, as well as gopher snakes were seen in this area.

_Juniper--Pinyon--Bitterbrush_

Three pairs of traplines were run from August 7-9, 1962, in a juniper-pinyon-bitterbrush stand on the southern end of Wetherill Mesa, starting 200 yards southwest of Double House (Fig. 1).

The forest on the southern end of the mesas consists of widely-spaced trees, which reflect the low amounts of precipitation at these lower elevations. Juniper trees are more numerous than pinyons, and both species are stunted in comparison to trees farther north on the mesa. _Purshia tridentata_ (bitterbrush) is the understory codominant. _Artemisia nova_ (black sagebrush) is present and grasses are the most abundant plants in the ground cover. Herbaceous species in the sparse ground cover include the following:

_Opuntia polyacantha_
_Solidago petradoria_
_Lathyrus pauciflorus_
_Penstemon linarioides_
_Lupinus caudatus_
_Yucca baccata_
_Phlox hoodii_

Only _P. maniculatus_ was caught in this stand; all mice were caught in the first night of trapping.

Five areas were selected for trapping in the summers of 1963 or 1964, in order to test hypotheses concerning habitat preferences of each of the species of _Peromyscus_. Four of these areas appeared to be ideal habitat for one species, but not for the other. The fifth area was expected to produce both species of _Peromyscus_. Each of these areas is discussed below.

_One Mile Southeast of Park's Entrance_

A small stand of _Artemisia tridentata_, occurring one mile southeast of the entrance to the park, is bordered to the north and northeast by a grassy meadow, discussed in the following account. Kangaroo rats have been reported in this general area, and I wanted to determine whether _P. maniculatus_ and _Dipodomys_ occurred together there. Fifty trap nights in this sagebrush, on June 20, 1963, yielded only _P. maniculatus_ (Table 1).

_Meadow, One-Quarter Mile Southeast of Park's Entrance_

A grassy meadow lies just to the east of the highway into the park, one-quarter of a mile southeast of the park's entrance. On July 30, 1963, one hundred traps were placed in two lines through the meadow, and were run for one night. Only individuals of _P. maniculatus_ were caught (Table 1).

_M-2 Weather Station, Chapin Mesa_

The M-2 weather station of the Wetherill Mesa Archeological Project was on the middle of Chapin Mesa at an elevation of 7,200 feet. This site was in an old C. C. C. area, about one mile north of the park's U. S. Weather Bureau station. The vegetation surrounding the M-2 site was a pinyon-juniper-muttongrass association. It was thought that both species of _Peromyscus_ would occur in this habitat.

On May 10, 1964, 25 traps were placed in this area and were run for one night. Only individuals of _P. truei_ were caught (Table 1).

_Grassy Meadow, Southern End Moccasin Mesa_

This large meadow is located eight miles south of the northern rim of Moccasin Mesa. The meadow lies in a broad, shallow depression that forms the head of a large drainage (Fig. 1). To the south of the meadow the drainage deepens, then reaches bedrock as it approaches the pour-off.

On August 23, 1964, one hundred traps were set in pairs in a line through the middle of the meadow; adjacent pairs were 20 feet from each other. Only individuals of _P. maniculatus_ were caught (Table 1).

Grasses are dominant in the ground cover, and _Sphaeralcea coccinea_ (globe mallow) is codominant. The abundance of globe mallow is due to the present and past disturbance of this meadow by a colony of pocket gophers. Trees are absent in the meadow. Species of plants include the following:

_Opuntia polyacantha_
_Chenopodium_ sp.
_Artemisia ludoviciana_
_Chrysothamnus nauseosus_
_Koeleria cristata_
_Poa pratensis_
_Lupinus ammophilus_
_Calochortus gunnisonii_
_Erigeron speciosus_
_Gutierrezia sarothrae_
_Tetradymia canescens_
_Tragopogon pratensis_
_Bromus tectorum_
_Sphaeralcea coccinea_
_Eriogonum racemosum_
_Polygonum sawatchense_
_Comandra umbellata_
_Penstemon strictus_

_Bedrock Outcroppings, Southern End Moccasin Mesa_

Two miles south of the preceding site, much of the mesa is a wide expanse of exposed bedrock, which extends approximately 100 feet inward from the edges of the mesa. Pinyon-juniper-mixed shrub woodland adjoins the bedrock.

On August 23, 1964, 25 traps were placed along the bedrock, near the edge of the forest. Only two mice, both _P. truei_, were caught. (Table 1).

HOME RANGE

In order to learn how extensively mice of different ages travel within their habitats, whether their home ranges overlap, and how many animals live within an area, it was necessary to determine home ranges for as many mice, of each species, as possible (Hayne, 1949; Mohr and Stumpf, 1966; Sanderson, 1966).

In 1961, the Colorado Department of Fish, Game and Parks established a permanent trapping grid in the area south of Far View Ruins (Fig. 1). The grid was constructed and used by Mr. Harold R. Shepherd, Senior Game Biologist, and his assistant, in the summers of 1961 and 1962, in a study concerning the effect of rodents on browse plants used by deer. The Department of Fish, Game and Parks allowed me to use the grid during 1963 and 1964, and also permitted me to use its Sherman live traps.

The grid is divided into 16 units, each with 28 stations (Fig. 2). Traps at four stations (1a, 1b, 1c, 1d) are operated in each unit at the same time, with two traps being set at each station. The traps are moved each day in a counter-clockwise rotation to the next block of four stations (2a, 2b, 2c, 2d) within each unit. The stations are arranged so that on any given night, traps in adjacent units are separated by at least 200 feet. As a result, animals are less inclined to become addicted to traps, for even within one unit they must move at least 50 feet to be caught on consecutive nights.

Traps were carefully shaded and a ball of kapok was placed in each trap to provide protection against the killing temperatures that can develop inside. In spite of these precautions, mice occasionally succumbed from heat or cold. The traps were baited with coarsely-ground scratch feed.

Mammals trapped in the grid were inspected for molt, sexual maturity, larvae of botflies, anomalies, and other pertinent data. Each animal was marked by toe- and ear-clipping and then released. Four toes were used on each front foot, and all five toes were used on each hind foot; two toes were clipped on the right front foot to signify number nine. The tip of the left ear was clipped to signify number 100, and the tip of the right ear was clipped to signify 200. If 300 or more animals had been captured, the tip of the tail would have been clipped to represent number 300. A maximum of 799 animals could have been marked with this system, which was used by Shepherd. I continued with it, starting my listings with number one.

Only two mice were caught that had been marked in the previous season by Shepherd.

Live traps were operated in the trapping grid from July 9 through October 25, 1963, and from June 25 through August 21, 1964. Traps were rotated through all stations five different times (35 days) in 1963, and twice (14 days) in 1964. Approximately three man hours were required each day to service and rotate the traps to the next group of stations. By the autumn of 1964, a total of 282 mice had been captured, marked and released; these were handled 817 times. In 1963, 235 mice were caught for an average of 20 captures per day; in 1964, 47 mice were caught for an average of 9 captures per day.

Calculations of Home Range

A diagrammatic map of the trapping grid was drawn to scale with one centimeter equal to 100 linear feet. Trapping stations were numbered on the diagram to correspond with stations in the field. An outline of this drawing also was prepared to the same scale, but station numbers were omitted. Mimeographed copies of such a form could be placed over the diagrammatic map and marks made at each station where an animal was caught. A separate form was kept for each animal that was caught four or more times.

In calculating home range, it was assumed that animals would venture half-way from the peripheral stations, at which they were caught, to the next station outside the range. A circle having a scaled radius of 25 feet (half the distance between stations) was inscribed around each station on the periphery of the home range by means of a drafting compass. The estimated range for each animal was then outlined on the form by connecting peripheries of the circles. Both the inclusive boundary-strip method and the exclusive boundary-strip method (Stickel, 1954:3) were used to estimate the ranges. The area encompassed within the home ranges was measured by planimetering the outline of the drawing. At least two such readings were taken for each home range; then these planimeter values were converted into square feet.

The customary practice in delimiting home ranges on a scaled map of a grid is to inscribe squares around the peripheral stations at which the animal was trapped, and then to connect the exterior corners of these squares (Stickel, 1954:3). If the distance between stations was 50 feet, such squares would have sides 50 feet long. An easier method is to inscribe a circle having a scaled radius of 25 feet around the peripheral stations by means of a drafting compass. To my knowledge this method has not been used previously and consequently has not been tested by experiments with artificial populations.

To test the accuracy of this method, a "grid of traps" was constructed by using 8-1/2 by 11 inch sheets of graph paper with heavy lines each centimeter. The intersects of the heavier lines were considered as trap stations. A "home range" of circular shape, 200 feet (4 cm.) in diameter, with an area of 31,146 square feet (0.71 acre), was cut from a sheet of transparent plastic. Another "home range" was made in an oblong shape with rounded ends. This range measured 2 by 65 centimeters (100 by 325 feet) and had an area of 32,102 square feet (0.74 acre). Each plastic range was tossed at random on sheets of graph paper for fifty trials each. The range was outlined on the graph paper, then circles having a scaled radius of 25 feet were inscribed around each "trap station" within the range. The peripheries of the inscribed circles were then connected and the estimated home range was delimited by the exclusive boundary-strip method. The estimated range was measured by planimetering, and the data were compared with the known home range (Table 2).

It was found that when calculated by the exclusive boundary-strip method, the circular home range was overestimated by 2.22 per cent. The oblong home range was overestimated by only 1.50 per cent. Stickel (1954:4) has shown that the exclusive boundary-strip method is the most accurate of several methods of estimating home ranges, and in her experiments this method gave an overestimate of two per cent of the known range. Thus, my method of encircling the peripheral stations yields results that are, on the average, as accurate as the more involved method of inscribing squares about the trap stations, and saves a great deal of time as well. My method probably yields better accuracy; a perfect circle is easily drawn by means of a compass, whereas a perfect square is more difficult to construct without a template.

It is generally understood that the estimated home range of an animal tends to increase in size with each additional capture; this increase is rapid at first, then slows. Theoretically, the more often an animal is captured, the more reliable is the estimate of its home range. Most animals, however, rarely are captured more than a few times. The investigator must decide how many captures are necessary before the data seem to be valid for estimating home ranges.

An animal must be trapped at a minimum of three stations before its home range can be estimated, and even then the area enclosed in the triangle will be much less than the actual home range. Some investigators have plotted home ranges from only three captures (Redman and Selander, 1958:391), whereas others consider that far more captures are needed to make a valid estimate of range (Stickel, 1954:5).

TABLE 2--Summary of Data from Experiments in Calculating Home Ranges
for an Artificial Population.

=======+========+=========+==========+========+================+========
| | | | Actual | Calculated |
| No. | Trap | Shape | area | area of range |
Series | of | spacing | of | of | by exclusive | +- S. D.
| trials | in ft. | range | range | boundary-strip |
| | | | in ft. | method |
-------+--------+---------+----------+--------+----------------+--------
A | 50 | 50 | Circular | 31,146 | 31,782 | 9,600
B | 50 | 50 | Oblong | 32,102 | 32,583 | 9,466
-------+--------+---------+----------+--------+----------------+--------

In my study, 161 individuals of _P. truei_ were caught from one to 13 times each. The estimated home ranges of 10 individuals of _P. truei_, each caught from eight to 13 times, were plotted and measured after each capture from the fourth to the last. The percentage of the total estimated range represented by the fourth through tenth captures was, respectively, 52, 65, 73, 85, 88, 93, and 96 per cent.

Ninety-seven individuals of _P. maniculatus_ were caught from one to 10 times each. For five individuals that were each caught from seven to 10 times, the percentage of total estimated range represented by the fourth through seventh captures was, respectively, 59, 69, 85, and 93 per cent.

The above percentages do not imply that the true home range of individuals of these species can be reliably estimated after seven or 10 captures; the average percentages do, however, indicate a fairly rapid increase in known size of home ranges between the fourth and tenth captures. The estimated home ranges of _P. maniculatus_ tended to reach maximum known size at about seven captures, whereas the estimated ranges of _P. truei_ tended to attain maximum known size after nine or more captures. The controversy over the number of captures of an individual animal required for a reliable estimate of its home range was not settled by my data.

I initially decided to estimate home ranges for animals caught five or more times and at three or more stations. Of the 282 animals caught and marked, only 48 were caught five or more times. Because of the small numbers of _P. maniculatus_ that were caught five or more times, I wanted to determine whether mice caught four times had an estimated range that was significantly smaller than that of mice caught five times. Eight individuals of _P. maniculatus_ were caught four times each, and it seemed desirable to use the data from these mice if such use was justified. Data from the 48 mice caught five or more times were used for this testing.

By means of a T-test, I compared the estimated ranges of those 48 mice following their fourth capture with ranges estimated after the fifth capture. The results did not demonstrate significant differences between the two sets of estimates; therefore, I decided to use data resulting from four or more captures, and at three or more stations.

Table 3 shows estimations of the home ranges of males and females of each species of _Peromyscus_. When the inclusive boundary-strip method is used, the area encompassed by the range tends to be larger than the area of the same range when estimated by the exclusive boundary-strip method. Stickel (1954:4) has shown that the inclusive boundary-strip method overestimates the home range by about 17 percent.

Analysis of Home Range by Inclusive Boundary-Strip Method

When all age groups were considered, the ranges of 16 males of _P. truei_ averaged 20,000 to 80,000 square feet (ave. 47,333; S. D. 19,286). The sizes of home ranges were not significantly different (P > 0.05) between adult and subadult (including juveniles and young) males.

All females of _P. truei_ (22) had ranges encompassing 16,666 to 83,333 square feet (ave. 40,666; S. D. 17,566). Sizes of home ranges between adult and non-adult females did not differ significantly. The mean range of adult males of _P. truei_ did not differ from that of adult females (P > 0.05).

Fifteen males of _P. maniculatus_ had ranges of 16,666 to 66,666 square feet (ave. 34,222; S. D. 16,000); six adult males had ranges of 33,333 to 53,333 square feet (ave. 38,666). Sizes of home ranges of adult and non-adult males of this species did not differ significantly.

Five females of _P. maniculatus_ had ranges of 33,333 to 76,666 square feet (ave. 51,333; S. D. 15,913); of these, four adults had ranges of 33,333 to 53,333 square feet (ave. 45,000). Sizes of home ranges of adult males of this species did not differ (P > 0.05) from those of adult females.

The ranges of adult males of _P. truei_ were compared with ranges of adult male of _P. maniculatus_; likewise the ranges of adult females of each species were compared. In each case no difference was demonstrable in sizes of ranges between the species.

The largest home range of any _P. truei_ was that of animal number 18, a young male with an estimated home range of 133,333 square feet. This animal was caught only five times, and his home range appeared unusually large in relation to that of other young males of this species; hence some of the widely-spaced sites of capture probably represent excursions from the animal's center of activity, rather than the true periphery of his range. These data were, therefore, not used in further computations. Stickel (1954:13) pointed out the advisability of removing such records from data to be used in calculations of home range.

Number eight had the largest home range of any female of _P. truei_; she was captured ten times, and had a range of 83,333 square feet. The vegetation within her range was pinyon-juniper woodland with understories of _Amelanchier_, _Artemisia nova_ and _Purshia_. Most of her home range was in the western half of unit H, but extended into parts of units D, I, G and N.

The largest home range for adult males of either species was number three of _P. truei_; he had a range of 80,000 square feet. The largest range for an adult of _P. maniculatus_ was 66,666 square feet (Table 3).

Analysis of Home Range by Exclusive Boundary-Strip Method

Stickel (1954:4) has shown that under theoretical conditions the exclusive boundary-strip method is the most accurate of several methods of estimating home range. This method overestimates the known range by only two percent.

Table 3 shows a comparison of home range calculations obtained for each species, when calculated by inclusive and exclusive boundary-strip methods.

The data for males and for females of each species were compared in the same manner as in the inclusive boundary-strip method. The ranges of 16 male individuals of _P. truei_ encompassed 14,000 to 56,666 square feet (ave. 34,333; S. D. 13,266); of these, the ranges of 10 adult males were from 23,333 to 53,333 square feet (ave. 39,733). Twenty-two females of this species had ranges of 13,333 to 50,000 square feet (ave. 27,199; S. D. 8,820). Eighteen adult females had the same extremes, but the average size of range, 28,000 square feet, was larger. Sizes of home ranges of males and females did not differ significantly.

The ranges of fifteen males of _P. maniculatus_ encompassed 13,333 to 46,666 square feet (ave. 26,666; S. D. 10,180). Of these, six adults had the same extremes in range, but an average size of 31,440 square feet.

The ranges of five females of _P. maniculatus_ varied from 28,000 to 53,333 square feet (ave. 37,199; S. D. 10,140). All but one of these females were adults. The sizes of home ranges of males and females did not differ significantly. No differences were found when ranges of adult males, or adult females, of both species were compared.

Adjusted Length of Home Range

The adjusted length of the range also can be used as an expression of home range. In this method, one-half the distance to the next trapping station is added to each end of the line drawn between stations at either end of the long axis of the range (Stickel, 1954:2).

The average length of home range for 15 males of _P. truei_ was 363 feet (S. D. 105 ft.); for 22 females of this species 326 feet (S. D. 94 ft.); for 14 males of _P. maniculatus_ 286 feet long (S. D. 94 ft.); and for four females of this species 347 feet (S. D. 83 ft.). The mean lengths of range of males and females differed significantly in _P. maniculatus_, but not in _P. truei_. However, no difference was demonstrable in mean sizes of ranges between males, or between females, of the two species.

Distance Between Captures

The distance between captures has been used by several investigators as an index of the extent of home range. More short than long distances tend to be recorded when traps are visited at random, and when inner traps of the range are more strongly favored (Stickel, 1954:10).

TABLE 3--Summary of Data for Estimated Home Ranges of Mice from a
Wild Population.

================+==================+=====+======+============+=========
| | | | Estimated |
Type of | Species | Sex | No. | home range | +- S. D.
Estimate | | | | in sq. ft. |
----------------+------------------+-----+------+------------+---------
Inclusive | _P. truei_ | M | 16 | 47,333 | 19,286
boundary-strip | " " | F | 22 | 40,666 | 17,566
| | | | |
| _P. maniculatus_ | M | 15 | 34,222 | 16,000
| " " | F | 5 | 51,333 | 15,913
----------------+------------------+-----+------+------------+---------
Exclusive | _P. truei_ | M | 16 | 34,333 | 13,266
boundary-strip | " " | F | 22 | 27,199 | 8,820
| | | | |
| _P. maniculatus_ | M | 15 | 26,666 | 10,180
| " " | F | 5 | 37,199 | 10,140
----------------+------------------+-----+------+------------+---------
Adjusted Length | _P. truei_ | M | 16 | 363 | 105
| " " | F | 22 | 326 | 94
| | | | |
| _P. maniculatus_ | M | 14 | 286 | 94
| " " | F | 4 | 347 | 83
----------------+------------------+-----+------+------------+---------

It is important to know approximately how far mice travel in one night. The distances traveled between captures on successive nights were calculated for all mice. Even animals caught most frequently usually were caught only once or twice on successive nights. Data from animals caught less than four times, and hence not usable for calculations of home range, could be used in calculating the distance between captures on successive nights. Thus the data were sampled in a more or less random manner for each species.

The mean distance traveled between captures on successive nights was determined for adult and non-adult animals (juvenile, young and subadult) of both sexes. Adult males of _P. maniculatus_ traveled an average of 151.66 feet (n = 24); young males of this species traveled an average of 134.28 feet (n = 7). Adult females of _P. maniculatus_ traveled 170.00 feet (n = 4); no data were available for young females.

Adult males of _P. truei_ traveled an average of 169.47 feet (n = 38); and young males traveled 159.44 feet (n = 18). Adult females of this species traveled 155.71 feet between captures (n = 35), while young females traveled 140.66 feet (n = 15).

The means were tested for differences in the distances traveled between young and adult males and between young and adult females of each species, as well as between males and between females of opposite species. In all cases, there were no demonstrable differences in the distance traveled between captures.

One of the more striking journeys between captures was that of number 59, a juvenal male of _P. maniculatus_, which traveled 1,070 feet between captures on July 16 and 17, 1963. The route between the two capture sites was over the most rugged part of the trapping grid. This datum was excluded from further calculations. The only other animal that approached this distance was a young female _P. truei_ that traveled 750 feet between captures.