(DRAFT) - Taxonomy
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
TAXONOMY
NAME - RAT, KANGAROO, FRESNO
OTHER COMMON NAMES - RAT, KANGAROO, FRESNO; RAT, KANGAROO, SAN JOAQUIN; RAT, KANGAROO and SAN JOAQUIN VALLEY
ELEMENT CODE -
CATEGORY - Mammals
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - MAMMALIA,
ORDER AND SUBORDER - RODENTIA,
FAMILY AND SUBFAMILY - HETEROMYIDAE,
GENUS AND SUBGENUS - DIPODOMYS,
SPECIES AND SSP - NITRATOIDES, EXILIS
SCIENTIFIC NAME - DIPODOMYS NITRATOIDES EXILIS
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Fresno Kangaroo Rat
Dipodomys nitratoides exilis Merriam, 1894
KINGDOM: Animal GROUP: Mammal
PHYLUM: Chordata CLASS: Mammalia
ORDER: Rodentia FAMILY: Heteromyidae
Except for its small size the Fresno kangaroo rat
(Dipodomys nitratoides exilis does not differ substantially from
other subspecies of D. nitratoides or the general form and appearance
of other species of kangaroo rats. It is adapted for bipedal
locomotion, having greatly enlarged hind limbs, a long tail, and a
short neck. The head is large and dorso-ventrally flattened and with
dorso-laterally placed ears and eyes. Dorsal and lateral surfaces are
colored dark yellowish-buff; the underparts are white. Dark whisker
patches are connected by a dark band of fur across the nose. The tail
has a crest of longer hairs distally, terminating in a tuft. Fresno
kangaroo rats are the smallest in size (and the smallest in the genus)
and have snuff-brown pelage and darker facial markings. D. n. exilis
is distinguised from the Tipton kangaroo rat (D. n. nitratoides)
and the short-nosed kangaroo rat (D. n. brevinasus) by its smaller
size. The length of hind foot (mm) in males and females,
Taxonomy - 1 (DRAFT) - Taxonomy
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
respectively, averages 33.9 and 33.4, as compared to the than 34.7 and
34.3 for males and females of the other subspecies (01). The skull is
shorter, with relatively less inflated mastoid bullae and shorter
rostrum and nasal bones than other taxon (01,02). D. n. exilis is
darker in color than "typical" D. n. brevinasus, but is about the same
shade as some populations of D. n. nitratoides.
Average and ranges of external and cranial measurements (mm)
of four D. n. exilis from Fresno, Fresno County, are: total length,
216 (211 to 226); length of tail, 128 (126 to 128); length of hind
foot, 33.3 (33 to 34); length of ear from crown, 8.5 (8 to 9);
greatest length of skull, 31.3 (30.7 to 32.7); breadth of skull
across bullae, 20.2 (20.0 to 20.6); breadth across maxillary arches,
17.4 (16.3 to 18.4); greatest length of nasals, 10.8 (10.2 to 11.4);
greatest width of rostrum near end, 2.8 (2.7 to 3.0); width of
maxillary arch at middle, 4.3 (4.1 to 4.5) (01). Mean and extreme
weights of two samples of males (n=30, 17) and females (n=27, 12),
respectively, are: 35 (23.9 to 45) 34.1 (30.7 to 39.3); and 31.1
(25 to 40), 29.7 (24 to 32).
At the time Merriam (03) described the Fresno kangaroo rat, he
considered it and other populations of D. nitratoides to be
subspecies of the Merriam kangaroo rat (D. merriami Mearns), a
widespread species occurring in the Mojave Desert of California and
elsewhere in western North America. Grinnell (01) recognized the San
Joaquin kangaroo rat as a species seperate and distinct from
D. merriami, a viewpoint that has been subsequently verified by
numerous researchers (04).
The subspecific status of D. nitratoides exilis has a more
complicated history. Merriam (03) described exilis and nitratoides
in the same publication. Grinnell (05) described
D. merriami brevinasus and later (06) separated all three taxa
from merriami. D. n. nitratoides and D. n. exilis are similar
in overall structure, and occupied contiguous geographic
ranges on the floor of the Tulare Basin in the San Joaquin Valley,
California. D. n. brevinasus exhibits greater differences from the
the other two subspecies, both in structure and in its habitat in the
foothills and higher valleys on the south and western fringes of the
Tulare Basin. Boolootian (07) studied structural variations in
populations of D. nitratoides, concluding that exilis did not merit
recognition as a subspecies and treated it as a synonym of
nitratoides. Hall and Kelson (08) did not follow Boolootians (07)
recommendation for reasons they attributed to the unpublished advice
of Seth Benson. Hoffmann (02), in an unpublished master's thesis,
studied the structural variation of D. nitratoides in more detail.
Hoffmann (02) concluded that Benson erred in his determination of the
identity of some San Joaquin kangaroo rats, but that exilis was
identifiable as a subspecies. Williams (04) agreed with Hoffmann's
(02) conclusions that the samples he regarded as exilis were distinct
from those he had available of nitratoides and brevinasus, but
considered the two subspecies to be partically indistinguishable when
samples of the populations from localities intermidate to the
geographic locations of Hoffmann's samples of exilis and nitratoides
were included.
The type locality for Dipodomys nitratoides exilis is Fresno,
Taxonomy - 2 (DRAFT) - Taxonomy
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
San Joaquin Valley, Fresno, California. The holotype, a young adult
male represented by the skin and skull collected in 1891, is in the
U.S. National Museum of Natural History, Washington D.C.
(no. USBM 34843/43823). Significant collections of specimens of
D. n. exilis are in the U.S. National Museum, Museum of Vertebrate
Zoology (Univ. Calif., Berkeley), and California State University,
Fresno. Hoffmann (02) provided the most comprehensive review of the
taxonomy of D. n. exilis, and listed tables of measurements for
samples of exilis, nitratoides, and brevinasus. Boolootian's (07) is
the most recent published source of information on the taxonomy of
D. nitratoides; he also gave measurements useful in distinguishing
subspecies (also see 01, 04, and 09).
San Joaquin kangaroo rat and San Joaquin Valley kangaroo rat
are other common names applied to the species D. nitratoides without
regard to subspecies. The common name, Fresno kangaroo rat, is
also applied to the species as a whole by some mammalogists,
generating confusion.
Taxonomy - 3 (DRAFT) - Status
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Fresno kangaroo rat (Dipodomys nitratoides exilis) has been
designated as Endangered pursuant to the Endangered Species Act
of 1973 (50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C.
1531-1540), as amended. The subspecies has this status wherever found
including the State of California. Critical Habitat has been
designated at T14S, R15E, E1/2, NW1/4 and NE1/4, Sec. 11, that part
of W1/2 Sec. 12 north of the Southern Pacific Railroad, E1/2, Sec. 12;
T14S, R16E, that part of Sec. 7 south of the Southern Pacific
Railroad, in Fresno County, CA (50 CFR 17.95(a)).
This subspecies is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.), which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
DOD -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public land under their control. Also responsible for
management/recovery on Department of Defense lands.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
Status - 1 (DRAFT) - Status
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
STATE: California
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: Calif. Dept. of Fish and Game
STATE STATUTE: Calif. Endangered Species Act; Fish and Game Code
Chap. 1.5, Art. 1, Sect. 2050.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
None.
ECONOMIC STATUSES:
The Fresno kangaroo rat's seed-caching behavior may be important
in the dispersal and germination of some plants, and their burrowing
and digging may have important beneficial effects on soil structure
and fertility (04).
82/12/30:47 FR 58454/58460 - Listed as a Category 1 species
83/11/21:48 FR 52608/52611 - Proposed Rule Endangered w/ Crit. Hab.
84/02/09:49 FR 04951/ - Re-opened public comment period
85/01/30:50 FR 04222/04226 - Final Rule - Endangered w/ Crit. Hab.
Status - 2 HABITAT ASSOCIATIONS
HABITAT - TERRESTRIAL
TERRESTRIAL
INLAND AQUATIC
LAND USE -
Transportation, communications, and Util
Cropland and Pasture
Orchards, Groves, Vineyards, Nurseries,
Herbaceous Rangeland
Mixed Rangeland
Streams and Canals
Nonforested Wetland
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Palustrine SS1
COMMENTS ON HABITAT ASSOCIATIONS -
The historic geographic range of the Fresno kangaroo rat
encompassed an area of grassland and alkali sink plant communities
on the San Joaquin Valley floor. Here, mean annual temperature is
about 17 deg. C (63 deg. F) with a mean monthly low of 7.1 deg. C
(46 deg. F) in January and a mean monthly high of 27.2 deg. C
(81 deg F) in July. Average annual percipitation varies from about
17.8 cm (7 inches) in the western part of the range to 27.9 cm
(11 inches) in the east, at Fresno. The mean frost-free period ranges
from about 225 to 250 days (18). The climate is hot and dry between
May and October, with little or no rainfall, and cool and moist from
November to April. In the winter months, from mid- or late November
through January, ground or Tule fogs frequently obscure the sun and
result in lower daytime temperatures. Freezes are relatively rare.
Soils in which Fresno kangaroo rats burrow typically remain
moist most of the year, except for a dry crust on the surface.
Alkaline vernal pools and temporary playas are typical features of
the terrain inhabited by Fresno kangaroo rats.
Extant habitat of Fresno kangaroo rats consists of arid,
alkaline, annual grasslands and shrubland associations between 60 and
90 meters (200 to 300 feet) above sea level. Surrounding lands
are under intensive irrigated and rotation farming (crops include
corn, cotton, soybeans, hay, grapes and other fruits, vegtables, and
pasture for grazing). Populations of D. nitratoides, considered to
belong to the exilis subspecies, have been taken in
iodine bush (Allenrolefea) associations that are typically flooded
yearly between about October - March. The only refuge not
inundated are on the dikes between flooded cells (04,17). Most
extant habitat has a sparse cover of plants and alkaline soils
with a high clay content, and is often nearly level. Most of
this ground is subject to seasonal flooding. Fresno kanagroo rats
prefer to locate burrows in natural areas above the flood levels, the
mounds around the bases of shrubs where wind-deposted soil has
accumulated, and in raised structures such as berms of roads and banks
of railroads and canals. Fresno kangaroo rats are driven out of areas
by flooding. Although soils in most extant habitat are relatively
high in silts and clay, prime habitat, supporting dense populations
had more friable soils with greater percentages of sands (11).
Areas of dense herbaceous vegetation and plant litter are not
Habitat Associations - 1 favored by kangaroo rats in general, nor by Fresno kangaroo rats (12).
Periodic fires or light-to-moderate grazing probably enhances habitat
for Fresno kangaroo rats by reducing density of vegetation and
accumulated litter and by promoting the growth of annual forbs.
Prominent plants associated with Fresno kangaroo rats include: brome
grasses (Bromus mollis, B. rubens), filaree (Erodium spp.), foxtail
fesque (Vulpia myuras), grasses such as Festuca megalura and
Hordeum spp., iodine bush (Allenrolfea occidentalis), pepper grass
(Lepidium nitidum), saltbush (Atriplex spp.), seepweed
(Suaeda fruticosa), shepard's purse (Capsella bursa-pastoris), and
wild oats (Avena fatua) (07,11,12,15).
Habitat Associations - 2 (DRAFT) - Food Habits
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
HERBIVORE
LIFESTAGE FOOD FOOD PART
General Roots/Tubers/Rhizomes-Herbaceous
General Poaceae
General
General Forb Leaves/Stems
General Forb Flowers/Fruit/Seed
General Deciduous Shrubs-Flowers/Fruit/Seed
General Evergreen Shrubs-Flowers/Fruit/Seed
General Arthropods
Food Habits - 1 (DRAFT) - Environment Associations
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Terrestrial Features: Depressions
G
G Terrestrial Features: Burrows
Environment Associations - 1 (DRAFT) - Life History
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
Little detailed information on the food habits of the Fresno
kangaroo rats is available. Seeds are the staple diet of Dipodomys
nitratoides (04,11,20). A wide variety of seeds are probably
consumed, including seeds of annual and perennial grasses,
particularly wild oats, brome grasses, soft chess, and wild barley
and fesque. Seeds of annual forbs such as filaree, peppergrass, and
shepard's purse are also important foods. Seeds of woody shrubs,
especially Atriplex spp. are diligently sought out by Tipton and
short-nosed kangaroo rats, and are also probably important for
Fresno kangaroo rats (19). Culbertson (11) found a few seed caches
in excavated burrows of Fresno kangaroo rats and remarked that they
probably ate green vegetation. Eisenberg (20) found that short-nosed
kangaroo rats ate green vegetation in captivity, and also consumed
insects (mealworm larvae). Captive D. nitratoides seem especially
fond of leaves and immature seed heads of filaree and sprouts of
a variety of seeds, and they also eat celery stems and leaves,
lettuce, apples, stolons and rhizomes of perennial grasses, and
several kinds of seeds, including oat, millet, and sunflower. They
did not eat the leaves of perennial grasses provided in captivity,
however (19).
Most kangaroo rats gather seeds when they are available and
cache them for consumption later. Typically, caches are made in small
pits that hold the contents of two seed pouches. Caches are located
on the surface of the soil, and are typically scattered over the
home range of the individual. Larger caches are often made in
chambers within the individual's burrow system, and smaller caches are
made in the walls of the burrows. These small caches also hold only
about the contents of two cheek pouches. The only types of caches
that have been found for the Fresno kangaroo rats are the small
caches in the sides of the burrows. Culbertson (11) speculated that
Fresno kangaroo rats did not cache seeds in their burrows to the same
extent as other kangaroo rats because the soil where they lived was
damp much of the year. Seeds would spoil rapidly under such
conditions. He further speculated that Fresno kangaroo rats therefore
were obligated to forage on the surface year-round, to a greater
extent than kangaroo rats which cached more food. In fall and winter,
after the wet season commences, sprouts of seeds and tender new growth
of grasses and forbs may be essential items in the diet of the Fresno
kangaroo rats. Green, developing seed heads may be important in the
spring months. Seeds, and perhaps insects, are the most important
items in the diet in late spring, summer, and fall. The Fresno
kangaroo rat can tolerate a lack of water for extended periods without
signs of stress (11 in 16).
HOME RANGE/TERRITORY:
No specific information is available on home range size and
territoriality in Fresno kangaroo rats or other populations of
Dipodomys nitratoides. Kangaroo rats in general are at least
territorial for part of the year, with females being more strictly
territorial then males. Home range size varies by habitat quality
Life History - 1 (DRAFT) - Life History
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
and species of kangaroo rat. In the closely related species,
D. merriami, size of home range averaged about 1.65 ha (4.06 acres)
for males and 1.57 ha (3.9 acres) for females in a study in New
Mexico (21). In contrast, the giant kangaroo rat, living in
association with D. n. brevinasus on the Carrizo Plains, had a home
range of about 0.04 ha (about 0.1 acre) (22). The home ranges of
Fresno kangaroo rats probably are larger than D. ingens, a species
with extensive food caching and management behaviors, but smaller than
D. merriami reported by Blair (21).
The burrow system is the apparent focus of territoriality in all
kangaroo rats. Except for nursing young associated with females, each
burrow system is typically occupied by a single individual. Eisenberg
(20,23) maintained a breeding colony of D. n. brevinasus in captivity,
keeping several individuals together in the same, large cage,
suggesting that at least individuals of the this subspecies are more
tolerant of others when given sufficient space. Culbertson (11) found
that captive Fresno kangaroo rats always fought when placed together
in a small cage, and concluded that individuals were intolerant of
each other. The social relations of Fresno kangaroo rats in the
wild are unknown.
PERIODICITY:
Fresno kangaroo rats are nocturnal and active year round. Tappe
(24) reported seeing Tipton kangaroo rats (D. n. nitratoides)
emerge from their burrows and begin above-ground activities as early
as 7 minutes before sunset in early spring. Other kangaroo rats in
the San Joaquin Valley are sometimes seen above ground by day in
March and April (19), but this is considered to be rare and isolated
deviations from the typical nocturnal activity. No other information
has been recorded on the periodicity of natural populations of
D. nitratoides. Lockard and Owings (25) studied activity patterns of
a captive group of D. n. brevinasus, finding that animals were active
throughout the nighttime hours. No strong tendencies to avoid
activity during moonlight or to curtail "surface" activity during a
full moon were seen among captives.
MIGRATION PATTERNS:
Fresno kangaroo rats are not migratory.
COVER/SHELTER REQUIREMENTS:
The Fresno kangaroo rat is not a cover-dependent species. Dense,
herbaceous vegetation is generally avoided, and areas of high scrub
density usually have few individuals of D. nitratoides (04,19).
Plants associated with Fresno kangaroo rats seem important only as a
source of seeds for food, and perhaps to provide nesting material.
Nesting material is derived from dried stems and leaves of grasses
and other herbaceous plants. A sparse-to-moderate cover of shrubs may
provide some protection from aerial predators while active on the
surface, but this has not been shown in field studies.
Individuals shelter in ground burrows that are dug by them or
their predecessors. Burrows are virtually always found in relatively
light friable soils in raised areas. Historically, colonies were
densest in areas with sandy loam soils. The surface area covered by
Life History - 2 (DRAFT) - Life History
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
the burrow system of individual Fresno kangaroo rats generally
varies from about 2.1 to 3.7 m (7 to 12 feet) on a side. There are
usually two or three burrow entrances that slant gently underground,
and one hole that opens from a verticle shaft. Tunnels are about
51 mm (2 inches) in diameter and extend about 30.5 to 38.1 cm (12 to
15 inches) below ground. There may be several interconnecting
tunnels and numerous dead-end side branches. Culbertson did not find
nesting material or large caches in the few burrows that he excavated
(11).
REPRODUCTIVE SITE REQUIREMENTS:
Nothing is known about mating behavior of Fresno kangaroo rats
in the wild. Eisenberg (20) described mating behavior and care of
young in a captive colony of D. n. brevinasus, and Culbertson (11)
recorded observations on captive Fresno kangaroo rats, including young
born in captivity, which are the basis of the speculation here and
under the following section on "Reproductive Characteristics". Mating
probably takes place on the surface within the territory of the
female. Culbertson (11) did not locate nests in excavated burrow
systems and observed that captive, pregnant females usually did not
make nests before giving birth. He thought that this was because
they were greatly disturbed by capture and confinement shortly
before giving birth.
REPRODUCTIVE CHARACTERISTICS:
Based on a captive colony of D. n. brevinasus, Eisenberg and
Issac (23) reported that sexual maturity was attained in as little as
82 days. Pregnant female Fresno kangaroo rats have been taken in all
months except August and December (11,26); Culbertson (11) reported
that pregnant females were captured between February - March and
June - September. Pregnancies between June and September might
represent second or third litters for adult females, summer breeding
by young females born in the spring, or both. Females are probably
capable of breeding two or more times per year, but few individulas
probably live long enough to breed more than once or twice. Breeding
behavior is probably initiated in late fall or early winter after
onset of the rainy season. Nothing is known about pair bonds in wild
populations, but there are probably no lasting male/female pair bonds
formed. Females may breed with more than one male during estrus.
Most females born the previous season probably do not give birth until
mid-February or early March. Gestation was 32 days and young were
weaned at 21 to 24 days in a captive colony of short-nosed kangaroo
rats (23). Average litter size in captive Fresno kangaroo rats
reported by Culbertson (11) was about 2 (range, 1 to 3); Eisenberg
and Issac (23) found an average of 2.3 young per litter in captive
D. n. brevinasus (range, 1 to 3).
PARENTAL CARE:
Little information is available on parental care. Young are
born in the burrow, probably within a nest of dried, shredded
vegetation. Young remain in the burrow continuously until they are
fully furred and able to move about easily. Young animals are
probably about 3 to 4 weeks old when they are first found on the
Life History - 3 (DRAFT) - Life History
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
surface. Culbertson (11) believed that young Fresno kangaroo rats
were not found out of the burrow and foraging for themselves until
about 6 weeks old. Young are nursed while the female is resting in a
standing position, on her hind legs; the young lay under her and
nurse from either a pectoral or inguinal teat. The female readily
retrieves young that stray from the resting area (11). Weaning
occurred at 21 to 24 days in captive short-nosed kangaroo rats (23).
POPULATION BIOLOGY:
Based on limited information, populations of Fresno kangaroo rats
probably have an annual turnover, with individuals born in the spring
rarely surviving to breed the following spring, and individuals born
in summer and fall forming the majority of the spring breeding
population. Hoffmann (26) found that only 2 of 75 marked animals
were present on study plots through 4 trapping periods between
10 February and 28 December. Numbers were the lowest in April, prior
to dispersal of spring-born young, and peaked in May. By June,
juveniles comprised the majority of the population. Probably few
animals born the previous year are still present in the late summer
months. Maximum longevity in natural populations is probably between
12 and 18 months. Reproductive potential of Fresno kangaroo rats is
relatively low for rodents. Limiting factors on populations are
unknown, but availability of suitable sites for burrows, free from
winter flooding, probably is a major factor. No specific information
is available on limitations of food, although heavy grazing by
livestock reduces densities of kangaroo rats, suggesting that food
may be limiting in such situations. Likewise, there is no information
on the roles of disease and predation in the population dynamics of
Fresno kangaroo rats. Under the current conditions of small, isolated
and inbred populations, both are probably major threats. In one
study (26), population density was estimated to vary from about 16.7
to 24.8 Fresno kangaroo rats per ha (6.8 to 10.1 per acre) during a
period from February through December. Another study provided
estimates of from 4.9 to 17.1 per ha (1.7 to 6.9 per acre) at
different seasons.
Hoffmann (26) believed that competition with Dipodomys heermanni,
a larger, more widely distributed species which uses a broader range
of plant communities, might be an important factor in extirpation of
Fresno kangaroo rats from sites impacted heavily by grazing.
SPECIES INTERRELATIONSHIPS:
Within the alkali-sink plant associations, Fresno kangaroo rats
probably were the more numerous small mammal under natural conditions.
As such, they were a keystone species, providing a major source of
food for a variety of predators, including the endangered San Joaquin
kit fox (Vulpes macrotis mutica). Their burrows are used extensively
by the endangered blunt-nosed leopard lizard (Gambelia silus) and
other reptiles (04,11). Their seed-caching behaviors may be important
in the dispersal and germination of some plants, and their burrowing
and digging may have important beneficial effects on soil structure
and fertility (04).
Potential predators on Fresno kangaroo rats include: burrowing
owl (Athene cunicularia), barn owl (Tyto alba), badger (Taxidea
Life History - 4 (DRAFT) - Life History
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
taxus), coyote (Canis latrans), kit fox (Vulpes macrotis), western
rattlesnake (Crotalus viridis), and gopher snake (Pituophis
melonoleucus) (11 in 16).
OTHER LIFE HISTORY DESCRIPTORS:
All known information for the Fresno kangaroo rat has been
covered in the previous sections.
Life History - 5 (DRAFT) - Management Practices
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Suppressing wildfire
Beneficial Prescribed/controlled burning of habitat
Beneficial Controlling/Restricting Off-Road Vehicles
Beneficial Restricting/regulating human disturbance of populations
Beneficial Controlling water levels
Beneficial Land Acquisition
Beneficial Controlling/Restricting Herbicide Use
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Agricultural Practice
Beneficial Reforestation
Beneficial Transplanting wild animals
Beneficial Controlling/Removing Native Vertebrates
Beneficial Controlling/Removing Domestic Animals
Adverse Low Gene Pool
Existing Low Gene Pool
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Highway/Railroads
Existing Highway/Railroads
Adverse Soil compaction by heavy equipment in mine areas
Existing Soil compaction by heavy equipment in mine areas
Adverse Migration barriers
Existing Migration barriers
Adverse Competition
Existing Competition
Adverse Predator control
Existing Predator control
Adverse Grazing
Existing Grazing
Adverse
Existing
Adverse Suppressing wildfire
Existing Suppressing wildfire
COMMENTS ON MANAGEMENT PRACTICES -
At the time of its discovery, in 1891, the process of
cultivation of natural communities providing habitat for the Fresno
kangaroo rat was already underway, starting first along the eastern
margin of the valley on the soils best suited for agriculture and
progressively spreading farther onto the valley floor. Soon after its
discovery, populations of the Fresno kangaroo rat were extirpated
from the vicinity of the type locality. Efforts by Grinnell to
collect additional specimens of D. n. exilis in the habitat similar
to the type locality failed, and he considered the subspecies to be
extinct. In 1934, Culbertson (10) reported on populations of
D. nitratoides that he found farther south and west of the type
locality in poorer-drained and seasonally flooded alkaline-sink
communities. Later, in 1946, Culbertson (11) reviewed the history of
Management Practices - 1 (DRAFT) - Management Practices
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
cultivation of habitat for Fresno kangaroo rats, outlined what he
believed was its extant geographic range in 1946, and noted that all
of its habitat could be cultivated in the future. By 1974, known
habitat for Fresno kangaroo rats had been reduced and fragmented into
three major areas, primarily by cultivation, to approximately 5,920 ha
(14,618 acres) in Fresno County (12). Warner and Koos (13,14)
reported that heavy grazing adversely impacted populations of Fresno
kangaroo rats, and was a significant threat to extant populations in
remaining habitat. Competition with the larger species, Dipodomys
heermanni, was considered to be an additional factor in the decline of
Fresno kangaroo rat populations on heavily grazed land. D. heermanni
is more widely distributed, occupies a broader range of plant
communities, and is the only kangaroo rat found in some heavily grazed
areas that were previously occupied by Fresno kangaroo rats. Hoffman
and Chesemore (15) reported on a comprehensive survey of remaining
potential habitat in Fresno County for D. n. exilis, finding that only
2,396 ha (5,894 acres) remained in 1981. Of this total, 2,072 ha
(5,120 acres) was considered marginal because of heavy livestock
grazing; presence of Fresno kangaroo rats was not confirmed on any of
the nine isolated parcels comprising this total. They confirmed
presence of Fresno kangaroo rats only on about 324 ha (800 acres)
(15).
Creation and maintenance of disked fire-breaks for fire
suppression around the edges of uncultivated fields that provide
habitat for Fresno kangaroo rats has also reduced habitat and caused
direct mortality (incidental killing) in the Alakli Sink Ecological
Reserve, and eleswhere. The widespread use of rodenticides to control
California ground squirrels probably adversely impacted populations of
Fresno kangaroo rats, although the history and effects of rodenticide
use on inhabited rangelands have not been documented. Other factors
in loss and degradation of habitat have been the construction of
highways, railroads, and canals (passage barriers) that further
reduced habitat, created sources of mortality to populations living
along their edges, and fragmented and isolated populations.
Except for 376 ha (932 acres), remaining potential habitat for
Fresno kangaroo rats is owned and subject to heavy livestock use (16).
Threats to extant poulations stem primarily from continuing conversion
of habitat to cultivated agriculture, other land developments, and
heavy grazing. The fragmentation and isolation of extant habitat
resulting from these developments pose additional threats in the
form of loss of genetic diversity and excessive inbreeding in small
populations (low gene pool). Other potential threats are use of
rodenticides on private property, competition with Heermann's kangaroo
rats, and disease and predation, either of which has the potential to
extirpate small, isolated populations.
UNAPPROVED PLAN:
U.S. Fish and Wildlife Service. 1986. Recovery Plan for the
Fresno Kangaroo Rat, Dipodomys nitratoides exilis. Tech. Draft.
U.S. Fish and Wildl. Serv., Portland, OR. 94 pp.
The Fresno kangaroo rat may be considered for reclassification as
Management Practices - 2 (DRAFT) - Management Practices
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
threatened when sufficient acreage has been secured and managed to
maintain self-sustaining populations in two discrete reserves for
five consecutive years. Delisting may occur when a third reserve
has been secured and measures for long-term effective management of
populations and habitats have been imposed.
Each reserve must contain a minimum size of 600 contiguous
hectares (1,500 acres). The first reserve will include lands within
the designated Critical Habitat, including the Alkali Sink Ecological
Reserve. The other sites required for eventual delisting will be
more clearly defined pending results of inventories to locate and
estimate Fresno kangaroo rat populations and potential habitat outside
of the designated Critical Habitat.
The populations within these secured sites will be managed to
meet or exceed a minimum average density of 2.0 Fresno kangaroo rats
per hectare (5.0 acre), deemed sufficient to maintain a
self-sustaining population.
A step-downed outline of recovery efforts for the Fresno kangaroo
rat follows:
1. Implement protection afforded by existing Federal and State Laws.
2. Protect Fresno kangaroo rat populations within remaining extant
habitats.
A. Evaluate extent and condition of remaining habitats within
the historical geographic range.
B. Determine distribution and population densities within
remaining habitats.
C. Establish site protection priorities based on survey
results.
D. Select and secure habitats (through acquistion or
management agreements) for long-term protection.
3. Manage Fresno kangaroo rat habitats and populations.
A. Develop management strategies to minimize adverse effects
of natural factors on Fresno kangaroo rat populations and
habitats (i.e., maintain vegetational composition and
cover,and minimize competition within marginal habitat with
the Tulare kangaroo rat). (Management actions may include:
1). controlled burning to modify and maintain the
the optimum vegetation composition.
2). creation of elevated mounds in low lying areas
previously occupied by the species; and
3). manipulation of competing Tulare kangaroo rats and
their habitat to favor the Fresno kangaroo rat.
B. Develop procedures to minimize human-related impacts
(i.e., control/limit - livestock grazing; pesticide use;
detrimental agricultural practices such as watertable
drawdown, increased soil salinity, and pesticide/herbicide
run-off/drift; off-road vehicle use; and incorrect
burning to reduce noxious plant species such as Russian
thistle; and to develop a means to lower road mortalities
by providing under-road crossings or barriers.
C. Develop, test, and implement habitat restoration
techniques.
D. Obtain life history information.
Management Practices - 3 (DRAFT) - Management Practices
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
E. Evaluate need for reintroduction of Fresno kangaroo rats
to reestablish former populations (i.e., by translocation).
F. Develop and implement habitat management plans.
4. Refine prime objective as required to ensure recovery of the
species.
A. Monitor population size and trend on secured and unsecured
lands.
B. Evaluate habitat conditions on subject lands on an annual
basis.
C. Determine success of management actions to recovery of the
species.
D. Modify management actions as necessary to promote recovery.
5. Coordinate efforts to facilitate effective management and recovery
of the Fresno kangaroo rat.
6. Develop and implement information and education programs on
management and protection of the Fresno kangaroo rat and its
habitat.
The California Department of Fish and Game plans to undertake
field inventories in 1987 outside of the Alkali Sink Ecological
Reserve to locate additional populations.
Management Practices - 4 (DRAFT) - References
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Grinnell, J. 1922. A geographical study of the kangaroo rats
of California. Univ. of Calif. Publ. in Zool. 24:1-124.
02 Hoffmann, W.M. 1975. Geographic variation and taxonomy of
Dipodomys nitratoides from the California San Joaquin Valley.
Unpubl. M.A. thesis, Calif. State Univ., Fresno. 75 pp.
03 Merriam, C.H. 1894. Preliminary descriptions of eleven new
kangaroo rats of the genera Dipodomys and Perodipus. Proc. of the
Bio. Soc. of Wash. 9:109-116.
04 Williams, D.F. 1985. A review of the population status of the
Tipton kangaroo rat, Dipodomys nitratoides nitratoides. Final Rept.
10181-4861. U.S. Fish and Wildl. Serv., Sacramento, CA. 44 pp.
05 Grinnell, J. 1920. A kangaroo rat from the San Joaquin Valley,
Calif. Journ. of Mammalogy 1:178-179.
06 Grinnell, J. 1921. Revised list of the species in the genus
Dipodomys. Journ. of Mammalogy 2:94-97.
07 Boolootian, R.A. 1954. An analysis of subspecific variations in
Dipodomys nitratoides. Journ. of Mammology 35:570-577.
08 Hall, E.R., and K.R. Kelson. The mammals of North America. Ronald
Press, New York, I:1-546 + 79.
09 Hafner, M.S. 1979. Density, distribution, and taxonomic status
of Dipodomys nitratoides nitratoides Merriam, 1894 (Rodentia -
Heteromyidae). Draft Final Rept. Calif. Dept. Fish and Game,
Nongame Wildlife Investigations, Sacramento. 17 pp.
10 Culbertson, A.E. 1934. Rediscovery of Dipodomys nitratoides
exilis. Journ. of Mammalogy 15:161-162.
11 Culbertson, A.E. 1946. Observations on the natural history of
the Fresno kangaroo rat. Journ. of Mammalogy 27:189-203.
12 Knapp, D.K. 1975. The Fresno kangaroo rat study. Calif. Dept.
Fish and Game, Nongame Wildl. Invest., Final Rept., Proj. W-54-R-7,
Job I-1.8. 21 pp.
13 Warner, D. 1976. The effects of grazing on Dipodomys nitratoides
exilis, in an alkali sink community. Unpubl. M.A. thesis. Calif.
State Univ., Fresno. 91 pp.
14 Koos, K.A. 1977. The fresno kangaroo rat population survey, 1977.
Calif. Dept. Fish and Game, Nongame Wildlife Investigations,
Final Rept. 32 pp.
15 Hoffman, M.W., and D.L. Chesemore. 1982. Distribution and status
of the Fresno kangaroo rat, Dipodomys nitratoides exilis. Calif.
Dept. Fish and Game, Nongame Wildl. Invest., Draft Final Rept.,
32 pp.
16 U.S. Fish and Wildlife Service. 1986. Recovery plan for the
Fresno Kangaroo Rat, Dipodomys nitratoides exilis, Tech. Draft.
U.S. Fish and Wildl. Serv., Portland, OR. 94 pp.
17 Williams, D.F. Unpubl. data; specimens on deposit in mammal
collection at Calif. State Univ., Stanislaus, Turlock, CA.
18 National Oceanic and Atmospheic Administration. 1974. Climates
of the States. Vol. II - western states including Alaska and
Hawaii. Water Inform. Center, Inc., Port Washington, NY.
pp. 481-975.
References - 1 (DRAFT) - References
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
References - 2 (DRAFT) - References
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
19 Williams, D.F. [n.d.] Unpubl. observ. Turlock, CA.
20 Eisenberg, J.F. 1963. The behavior of heteromyid rodents. Univ.
Calif. Publ. in Zool. 69:1-100.
21 Blair, F.B. 1943. Populations of the deer mouse and associated
small mammals in the mesquite association of southern New Mexico.
Contrib. Lab. of Vert. Bio., Univ. of Mich. 21:1-40.
22 Braun, S.B. 1965. Home range and activity patterns of the giant
kangaroo rat, Dipodomys ingens. Journ. of Mammalogy 66:1-12.
23 Eisenberg, J.F., and D.E. Isaac. 1963. The reproduction of
heteromyid rodents in captivity. Journ. of Mammalogy 44:61-67.
24 Tappe, D.T. 1941. Natural history of the Tulare kangaroo rat.
Journ. of Mammalogy 22:117-148.
25 Lockart, R.B., and D.W. Owings. 1974. Moon-related surface
activity of bannertail (Dipodomys spectabilis) and Fresno
(D. nitratoides) kangaroo rats. Anim. Behaviour 22:262-273.
26 Hoffmann, W.M. 1974. The Fresno kangaroo rat study. Calif. Dept.
Fish and Game, Special Wildl. Invest., Final Rept., Project
W-54-4, Job 11-5.4. Sacramento. 23 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Hoffman, M.W., and D.L. Chesemore. 1982. Distribution and status
of the Fresno kangaroo rat, Dipodomys nitratoides exilis. Calif.
Dept. Fish and Game, Nongame Wildl. Invest., Draft Final Rept.
Sacremento. 32 pp.
02 Culbertson, A.E. 1946. Observations on the natural history of
the Fresno kangaroo rat. Journ. of Mammalogy 27:189-203.
03 Hoffmann, W.M. 1975. Geographic variation and taxonomy of
Dipodomys nitratoides from the California San Joaquin Valley.
Unpubl. M.A. thesis. Calif. State Univ., Fresno. 75 pp.
04 Knapp, D.K. 1975. The Fresno kangaroo rat study. Calif. Dept.
Fish and Game, Nongame Wildl. Invest., Final Rept., Proj. W-54-R-7,
Job I-1.8. 21 pp.
05 Williams, D.F. 1985. A review of the population status of the
Tipton kangaroo rat, Dipodomys nitratoides nitratoides. Final
Rept., 10181-4861. U.S. Fish and Wildl. Serv., Sacramento, CA.
44 pp.
06 Brode, J. 1985. Revised blunt-nosed leopard lizard essential
habitat maps: May, 1985. Unpubl. maps. Calif. Dept. of Fish and
Game, Sacramento.
07 Boolootian, R.A. 1954. An analysis of subspecific variations in
Dipodomys nitratoides. Journ. of Mammalogy 35:570-577.
08 Williams, D.F. Unpubl. data; specimens on deposit in mammal
collection at Calif. State Univ. - Stanislaus, Turlock.
09 Culbertson, A.E. 1934. Rediscovery of Dipodomys nitratoides
exilis. Journ of Mammalogy 15:161-162.
10 Hoffmann, W.M. 1974. The Fresno kangaroo rat study. Calif. Dept.
Fish and Game, Special Wildl. Invest., Final Rept., Project
W-54-4, Job 11-5.4. 23 pp.
11 Williams, D.F. Unpubl. data; specimens on deposite in mammal
collections at Calif. State Univ., Fresno, CA; Museum of Vertebrate
Zoology, Univ. Calif., Berkeley; and U.S. Nat. Museum, Wash., D.C.
References - 3 (DRAFT) - References
Species RAT, KANGAROO, FRESNO
Species Id ESIS051012
Date 14 MAR 96
References - 4