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Neotoma albigulaTurner Island woodrat(Also: white-throated woodrat)

By Maria Brym

Geographic Range

Neotoma albigula occupies a wide range of habitats in the southwestern United States and northern Mexico. The northern extent of its range includes the Four Corners region and the southernmost tip of Nevada. It can also be found as far west as southeastern California and as far east as central Texas. It is distributed widely throughout New Mexico and Arizona and through most of northern Mexico. (Cockrum, 1982; Macedo and Mares, 1988; Zeveloff, 1988)

Habitat

Neotoma albigula appears in a wide range of habitats including forest edges, scrubland forests, and low deserts, and can be found from 2135 m to 76 m in elevation. It occasionally builds dens in the caves of rocky hills, but more commonly prefers areas of extensive cholla and prickly pear cactus. Using cacti and other large desert plants as an anchor, N. albigula builds an extensive home using pieces of cacti, cow chips, sticks, bones, and any other found items, including garbage left by humans. It is known for its large and complex shelters. Averaging 8 feet in diameter and 2 to 3 feet in height, its shelters contain several chambers and underground tunnels which are used to escape predators. Each shelter also includes a small underground nest that serves as a retreat from daytime heat and as a place for females to raise their young. The size of the nest averages about 8 inches in diameter. It consists of soft materials such as grasses or shredded fibers. The average density of N. albigula shelters in heavily populated areas is between 5 to 15 per acre, but densities vary depending on resource availability. Neotoma albigula is a solitary species and houses are never cohabited by adults. (Brown, 1968; Hoffmeister, 1986; Macedo and Mares, 1988; Olsen, 1971)

  • Other Habitat Features
  • caves
  • Range elevation
    76 to 2135 m
    249.34 to 7004.59 ft

Physical Description

In general, Neotoma albigula has a medium-sized body with brownish gray fur covering dorsum. The venter is white or light gray with a white throat. The tail is shorter than the length of the body, is bi-colored and is covered in moderately long hair. The ears are large and hairless. Average mass is 197 g and average head-body length is 328 mm; however, body size varies depending on climate, with larger specimens found in colder regions and smaller specimens found in warmer regions. Black color-morphs of N. albigula occur on lava beds in Texas and New Mexico. The species is further divided into 13 subspecies that occupy overlapping ranges throughout the southwestern United States and northern Mexico. Subspecies are distinguished primarily by morphometric characteristics (e.g., body size). Average basal metabolic rate for this species is 36000 cm^3 oxygen/hour. Sexual dimorphism has not been documented in N. albigula. (Cockrum, 1982; Macedo and Mares, 1988; Zeveloff, 1988)

  • Average mass
    197 g
    6.94 oz
  • Average length
    328 mm
    12.91 in
  • Average basal metabolic rate
    36000 cm3.O2/g/hr

Reproduction

Mating the only time that Neotoma albigula engages in social behavior with adults conspecifics. Foot thumping often precedes copulation, although the purpose is unknown. During copulation, males and females have limited tactile contact and males do not clasp the female. The average copulatory lock lasts 30.1 seconds. It is hypothesized that this short lock has evolved to minimize predation risk as copulation can create vulnerability to attack. Mate selection behavior is not well understood. Neotoma albigula is promiscuous and no bonding occurs between mates after copulation. (Macedo and Mares, 1988)

Reports on the breeding season of Neotoma albigula vary greatly. Some observations suggest year-round breeding, while others identify a period between January and September as breeding season. This discrepancy may be a result of differences in breeding seasons among the different regions occupied and/or subspecies. However, all sources agree that breeding slows during the hottest months of the year and that the majority of breeding takes place between January and June. Neotoma albigula can produce multiple litters per season, and females are sometimes found with offspring of two different ages in their dens. Average gestation lasts 38 days, however, gestation periods short as 30 days have been recorded. Litters range from 1 to 4 offspring, with an average of 2 offspring per litter. Average birth mass is 10.9 grams. Weaning occurs between 62 and 72 days, at which point offspring have already begun practicing shelter construction and consuming cacti, berries, and vegetation. In the wild, N. albigula reaches sexual maturity at around 180 days. In captivity, instances of reaching sexual maturity as young as 80 days in females and 101 days in males have been documented. (Macedo and Mares, 1988)

  • Breeding interval
    Neotoma albigula can breed multiples times per season. Females have been discovered caring for neotatal young and partially mature young simultaneously.
  • Breeding season
    Breeding begins in January but generally slows in mid-summer and may ceases in August or September depending on region and climate. Some researchers report year-round breeding.
  • Range number of offspring
    1 to 4
  • Average number of offspring
    2
  • Range gestation period
    30 to 38 days
  • Range weaning age
    62 to 72 days
  • Average time to independence
    7 months
  • Range age at sexual or reproductive maturity (female)
    80 to 300 days
  • Average age at sexual or reproductive maturity (female)
    180 days
  • Range age at sexual or reproductive maturity (male)
    101 to 300 days
  • Average age at sexual or reproductive maturity (male)
    180 days

Male N. albigula play no role in rearing the offspring. Little is known about pre-conception preparation for reproduction by the female, although den construction could be considered part of her investment. As is the case for all mammals, the mother uses her body to protect the offspring in utero. After birth, a female lactates and feeds the offspring her milk for 62 to 72 days. She cares for and protects her young for approximately 6 months until they have reached maturity and disperse to build their own houses. A female can have more than one litter residing in her home at one time, but only one litter nurses at a time. Some subspecies are known to wean and mature earlier than average, reducing parental investment. (Olsen, 1971; Prakash and Ghosh, 1975)

  • Parental Investment
  • altricial
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

Little is known on the lifespan of Neotoma albigula. The few existing data suggests that members of this species can live between 3 and 5 years. Longest known lifespan in the wild is 6 years. (Zeng and Brown, 1989)

  • Range lifespan
    Status: wild
    72 (high) months
  • Typical lifespan
    Status: wild
    45 (high) months

Behavior

Neotoma albigula is primarily nocturnal, but some observors have reported daytime activity within the den. It remains active year round. As a solitary species, it has very limited social interactions; these occur between adults only during copulation. The only other social interaction experienced by N. albigula is that between a mother and her offspring. Foot thumping is thought to be a form of communication between conspecifics in N. albigula and has been observed prior to copulation and as a reaction to predatory threats. Offspring as young at 26 days old have been observed to participate in foot thumping as a reaction to predatory stimuli. (Cockrum, 1982; Macedo and Mares, 1988; Olsen, 1971)

Nest construction involves collecting many different items. Neotoma albigula constructs large nests that integrate cacti, sticks, animal bones, cow chips and man-made materials. Members of this species appear to have a particular affinity for collecting man-made objects for incorporation into the nest. See Habitat section for additional information. (Macedo and Mares, 1988)

  • Average territory size
    486 m^2

Home Range

Home ranges of Neotoma albigula average about 486 m^2 and nest densities average 5 to 15 every 4,000 m^2. Nests are separated by an average distance of 12 meters, causing many home ranges to overlap, which does not appear to be a source of agonistic behavior among residents. Territorial behavior near the nest has been observed. (Macedo and Mares, 1988; Olsen, 1971)

Communication and Perception

White-throated woodrats use scent to communicate with conspecifics. Males have specialized midventral glands that they use to scent mark selected locations. In females, this gland is poorly developed. Pheromones are used in social situations involving courtship, sexual, agonistic, hierarchical, and possibly territorial interactions. Pheromones present in feces are used to determine the sex of den occupants, thereby avoiding agonistic encounters between males. White-throated woodrats rely upon scent and visual cues to warn them of danger from predators. Altricial infants with unopened eyes cannot distinguish a predator by scent alone. (Macedo and Mares, 1988)

Food Habits

In desert habitats, Neotoma albigula feeds primarily on cholla and prickly pear cactus. Neotoma albigula is not an obligate drinker and acquires most of its water from cactus. Some observations estimate that the diet of N. albigula consists of up to 44% cacti. During periods of exceptionally high temperatures, N. albigula can eat upwards of 60% of its body mass in cacti per day. While this species prefers cacti, it is considered a generalist herbivore. Other important food items includes the beans and bark of mesquite plants, juniper branches and berries, various flowers, and yucca leaves. Neotoma albigula has also been observed consuming insects, small reptiles and mice, however, such observations are uncommon. Neotoma albigula is known to store food throughout its large shelter. (Macedo and Mares, 1988; Olsen, 1971; Zeng and Brown, 1989; Zeveloff, 1988)

  • Animal Foods
  • mammals
  • reptiles
  • insects
  • Plant Foods
  • leaves
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • flowers

Predation

Predators of Neotoma albigula include a number of mustelids such as weasels, skunks, and badgers. Additional mammalian predators include racoons, red fox, gray fox, bobcats, coyotes, and ringtails. Other important predators of N. albigula include snakes and Great-horned Owls (Davis, 1960; Hoffmeister, 1986; Macedo and Mares, 1988; Olsen, 1971; Prakash and Ghosh, 1975)

Altricial young are unable to identify predators by smell alone and treat predators as inanimate objects. Once their eyes are open, visual clues play an important role in predator detection for individuals as young as 26 days. In predatory experiments, the reaction of Neotoma albigula to predatory stimuli occurs in three steps: awareness of threat, foot thumping and increased agitation, and fast and random direction running. Structural adaptations to predation are thought to have lead to extensive tunnels and chambers in and around the habitation structures of N. albigula. Tunnels appear to function as a means of escape when faced with a potential threat in or near the nest. A large proportion of N. albigula's shelter is constructed from pieces of cacti. These spiny additions act as a deterrent for predators, without inhibiting the mobility of N. albigula. Nocturnal behavior likely reduces risk of predation. By remaining inside during the day, N. albigula avoids many predators including many bird species and other diurnal predators. The coloration of N. albigula likely helps camouflage them from potential predators as well. (Davis, 1960; Hoffmeister, 1986; Macedo and Mares, 1988; Olsen, 1971; Prakash and Ghosh, 1975)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The herbivorous diet of Neotoma albigula consists primarily of cacti, their fruit and other desert vegetation. Its diet can alter the vegetation profile of the local area and may facilitate seed dispersal. Shelter construction and fecal distribution can cause an increase in the amount of soluble salts, bicarbonates, and nitrates in the soil. Once abandoned, shelters can be inhabited by a range of species including other woodrats, desert reptiles , and numerous species of rodents. Parasites specific to N. albigula have not been documented. (Macedo and Mares, 1988; Prakash and Ghosh, 1975)

  • Ecosystem Impact
  • disperses seeds
  • creates habitat

Economic Importance for Humans: Positive

There are no known positive effects of Neotoma albigula on humans, however, there have been rare reports of humans consuming N. albigula. (Macedo and Mares, 1988)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Neotoma albigula causes damage to cabins and summer homes where it may occasionally nest in the absence of humans. Damage to furniture and other items that woodrats incorporate into nests is not uncommon, and significant amounts of fecal waste have been left in absent residences. Additionally, N. albigula has been known to raid food stores that are poorly sealed. (Macedo and Mares, 1988; Zeveloff, 1988)

  • Negative Impacts
  • household pest

Conservation Status

Neotoma albigula is widespread and abundant throughout its geographic range. As a result, this species is classified as "least concern" on the IUCN's Red List of Threatened Species.

Other Comments

Another common term for the white-throated woodrat is "packrat". This term refers to its tendency to cache man-made objects.

Contributors

Maria Brym (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

Berquist, P. 2000. "Neotoma Albigula" (On-line). Arizona-Sonora Desert Museum Digital Library. Accessed March 11, 2011 at http://www.desertmuseumdigitallibrary.org/public/detail.php?id=ASDM05440.

Brown, J. 1968. Adaptation to environmental temperature in two species of woodrats, Neotoma cinerea and N. albigula. Ann Arbor, MI: University of Michigan.

Cockrum, E. 1982. Mammals of the Southwest. Tucson, AZ: University of Arizona Press.

Davis, W. 1960. The Mammals of Texas. Austin, TX: The Information-Education Division of the Department of Wildlife Managment Agriculture and Mechanical College of Texas.

Hoffmeister, D. 1986. Mammals of Arizona. Tucson, AZ: University of Arizona Press.

Macedo, R., M. Mares. 1988. "Neotoma Albigula" (On-line pdf). Accessed April 04, 2011 at http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/.

Olsen, R. 1971. "SECONDARY HABITAT SELECTION IN THE WHITE-THROATED WOODRAT (NEOTOMA ALBIGULA)" (On-line pdf). Accessed March 11, 2011 at http://proquest.umi.com.proxy.lib.umich.edu/pqdweb?did=758221101&Fmt=7&clientId=17822&RQT=309&VName=PQD&cfc=1.

Prakash, I., P. Ghosh. 1975. Rodents in Desert Environments. The Hauge: W. Junk.

Zeng, Z., J. Brown. 1989. Comparative Population Ecology of Eleven Species of Rodents in the Chihuahuan Desert. Ecology, 70/5: 1507-1525.

Zeveloff, S. 1988. Mammals of the Intermountain West. Salt Lake City, UT: University of Utah Press.

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