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Neotoma micropussouthern plains woodrat

By Demetri Lafkas and Leila Siciliano Martina

Geographic Range

Southern plains woodrats (Neotoma micropus) have a range that extends north into southeastern Colorado and southwestern Kansas and south through western Oklahoma, western Texas and northeastern Mexico. They also inhabit the majority of New Mexico except the far northwestern portion of the state. (Braun and Mares, 1989; Thies and Caire, 1991)

Habitat

Southern plains woodrats prefer dry grassland environments, they favor cactus grasslands but can also be found in shrubby or mesquite grasslands, regardless, they are typically found in close proximity to shrubs or cacti. They are generally found in semi-arid, flat plains and low valleys, often located between timberlands and deserts, they may also be found on rocky hillsides. Most populations construct below ground dens, however, some populations are precluded from this behavior due to the soil quality in their area. Where den excavation is not possible, southern plains woodrats use rock crevices and trees for cover. (Braun and Mares, 1989; Charles, et al., 2012; Reid, 2006; Suchecki, et al., 2004)

Physical Description

Southern plains woodrats are medium-sized rodents with white feet, large ears, dark eyes and long whiskers. Their dorsal side has soft, dense, grayish, sometimes buffy fur, with occasional black hairs on their back. Their ventral side is gray with a white throat and pectoral region. Their tail is dark above and lighter on the bottom side, it is also short, heavy and mostly hairless. Males have an average total body length of 370 mm, including an average tail length of 152.6 mm, whereas females have an average total body length of 355.8 mm, including an average tail length of 147.1 mm. They have four digits on each foot. Their dental formula is 1/1, 0/0, 0/0, 3/3, with a total of 16 teeth. Individuals in coastal Texas and south-central Kansas tend to be larger than individuals in other populations. Southern plains woodrats show no sexual dimorphism in coloration. Although males tend to be somewhat larger than females, they show no significant sexual dimorphism in size. Adult animals molt each year, typically between June and October. Juveniles go through 2 to 3 molts before achieving their adult pelage. (Braun and Mares, 1989)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    180 to 317 g
    6.34 to 11.17 oz
  • Average length
    355 to 370 mm
    in

Reproduction

The mating behavior of southern plains woodrats is a long and detailed process. Males and females cautiously approach each other in a crouched position while partially flexing their legs. These animals then smell each other’s faces while touching their whiskers together, after which, they stand on their hind feet and touch their forefeet together while chattering their teeth. Individuals then bob their heads side to side and forward and back. The female quickly passes back and forth in front of the male in a crouched position, making short hops and rapidly drumming her hind feet. She then drags her back end on the ground, directing it toward the male while giving low-pitched raspy squeaks. The male approaches from the rear and mounts. The pair may continue to copulate every 2 to 10 minutes, prior to each mating attempt, the female performs a display. Copulation lasts from 2 to 90 seconds, but averages 10 to 20 seconds. Females may become pregnant with as little as 2 copulations, but they are much more reproductively successful with four or five copulations. Based on their home range distribution, these animals are assumed to engage in a promiscuous mating system. (Braun and Mares, 1989; Conditt and Ribble, 1997; Suchecki, et al., 2004)

Southern plains woodrats typically breed in the early spring and produce 1 litter per year. However, southern populations may produce 2 or more litters per year as a result of their continuous breeding season, which peaks in early spring and late fall. Their gestation period lasts about 33 to 35 days, after which, they have litters of 1 to 4 individuals, each weighing about 10 to 13 grams. Litters are most frequently composed of 2 to 3 individuals, although variation can be seen in populations, northern populations have an average of 3 individuals per litter while southern populations average 2. Males and females grow at a similar rate; however, by about 6 months old, males are generally somewhat larger. Technically, sexual maturity occurs at 10 weeks for males and 6 months for females, however, most individuals do not mate immediately after reaching maturity. (Braun and Mares, 1989; Pitts, et al., 1985)

  • Breeding interval
    Southern plains woodrats mate frequently during the breeding season.
  • Breeding season
    Most populations breed in the early spring, however, southern populations may have a continuous breeding season.
  • Range number of offspring
    1 to 4
  • Range gestation period
    33 to 35 days
  • Average weaning age
    30 days
  • Average time to independence
    30 days
  • Average age at sexual or reproductive maturity (female)
    6 months
  • Average age at sexual or reproductive maturity (male)
    10 weeks

There is currently very little information available regarding the parental behavior of southern plains woodrats. However, an endangered member of the same genus, Key Largo woodrats (Neotoma floridana), have been studied in the captive environment. Similar to southern plains woodrats, female Key Largo woodrats typically nurse and protect their young for approximately 30 days following parturition. Young are frequently seen grasping tightly to their mother's mammae, although suckling decreases over the 30 day nursing period. In the captive environment, female Key Largo woodrats were able to forage with and without suckling young; however, there is currently no information available regarding wild individuals. Occasionally, females forcibly remove the young from their mammae, although about 75% of the time they have at least one offspring attached. Young do not choose to leave the mammae until they are about 13 to 21 days old; they begin eating solid food around the same time. Dependent offspring are often observed licking their mother's mouth, the causes of this behavior are unknown, but it may either provide moisture or scent cues. No paternal care is provided in this genus. (Alligood, et al., 2008; Braun and Mares, 1989)

Lifespan/Longevity

Southern plains woodrats have a fairly short lifespan. Females tend to live longer, particularly among those that survive until adulthood. Due to high mortality among immature individuals, males have an average lifespan of 5.6 months and females have an average lifespan of 7.6 months. The average lifespan among individuals that survive to adulthood is not known. The oldest known individual survived to be about 2.25 years old. (Braun and Mares, 1989)

  • Range lifespan
    Status: wild
    27 (high) months
  • Average lifespan
    Status: wild
    5.6 to 7.6 months

Behavior

Southern plains woodrats are solitary and territorial except when mating. While some studies have failed to observe more than one adult woodrat in a nest at one time (Conditt and Ribble, 1997), others have observed an adult male and female residing in the same nest during the daytime (Suchecki et al. 2004). When no longer under maternal care, 65% of males and 38% of females disperse from their place of birth. Dens with 2 to 5 entrances are built underneath cacti or shrubs. Many individuals use the same den for life, particularly among females. When the soil is conducive, their underground dens are used for food storage, nesting and predator evasion. Their nest chamber is full of soft grasses and is kept free of food scraps and feces. Above ground, their nests are made of plant material and human trash, which has given them the nickname "packrat". Aggressive encounters may ensue when residents defend their territory. Southern plains woodrats are nocturnal and are most active between dusk and midnight. (Braun and Mares, 1989; Conditt and Ribble, 1997; Reid, 2006; Suchecki, et al., 2004)

  • Range territory size
    157.8 to 1,829.2 m^2

Home Range

Their home range sizes may vary based on the location of the population, regardless; males tend to have a much larger range size. In southwestern Texas, the average home range size ranged from 971.3 to 1,335.5 meters squared. However, the minimum required range space for males was 232.4 m2, compared to 157.8 m2 for females. Whereas the average range size in southern Texas was 1,696 to 1,829.2 m2 for males and 188 to 258.2 m2 for females. Likewise, the overall home range size in Guadalupe Mountains National Park is 258 m2. Home ranges may overlap; there are generally 0 to 31 individuals per hectare. Their daily movement is minimal, sticking to their cactus patch or a neighboring patch; they rarely cross areas without vegetation. Southern plains woodrats may have paths leading from their dens to many of their preferred feeding areas. (Braun and Mares, 1989; Linzey, et al., 2008; Suchecki, et al., 2004)

Communication and Perception

Scent marking is an important method of communication for woodrats. Southern plains woodrats are able to identify members of the opposite sex by scent. Males use urine and sebum to attract mates, while females use their urine and feces. Likewise, southern plains woodrats are extremely sensitive to sound. These animals quickly react to even the slightest sound or movement. They produce a drumming sound by hitting the ground with their hind feet; this may act as an alarm call or establish territory. Southern plains woodrats also have extremely acute vision, which may help them evade predators. (August, 1978; Braun and Mares, 1989; Reid, 2006)

Food Habits

Their diet consists of cactus leaves, cactus fruits, berries, mesquite pods and beans, acorns and other types of plant material. Some of their favorite food items include the joints, fruits, leaf blades and seeds of prickly pears (Opuntia) and Great Plains yuccas (Yucca glauca). They obtain their required water from the food they eat. During droughts, they depend on cactus pulp for food and moisture. These animals designate an area of their den for caching food. Southern plains woodrats are larder hoarders and begin collecting food stores in late summer and early autumn. Each year they typically lose a great deal of weight during autumn and winter and gain weight during the winter and spring. Occasionally, their caches are raided by other animals including Ord's kangaroo rats and hispid pocket mice. (Braun and Mares, 1989; Reid, 2006)

  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

Predation

Southern plains woodrats are preyed upon by many different animals. They are hunted by a variety of birds such as white-tailed hawks, Harris's hawks, great horned owls, barn owls and greater roadrunners, as well as a variety of mammal species including raccoons, bobcats, coyotes and foxes. Southern plains woodrats are also hunted by western rat snakes and western diamondback rattlesnakes, particularly in the southern part of their range. However, they may be immune to fairly large quantities of snake venom. Fire ants are also known to trap and kill adults and nestlings. To avoid predation, southern plains woodrats often hide in their dens. (Braun and Mares, 1989; Suchecki, et al., 2004)

Ecosystem Roles

Southern plains woodrats serve as important primary consumers throughout their range, consuming nuts, berries, leaves and many other types of vegetation. They also host many different species of parasites such as fleas, ticks, mites, lice, nematodes and protozoa. This species is an important ecological engineer. The microclimate created in their dens is essential for crickets, wolf spiders and lycid beetle larvae, likewise, 40 additional invertebrate taxa also casually use this habitat. Their dens are also by other vertebrate species as well including ornate box turtles, side-blotch lizards, gopher snakes, cactus mice and deer mice. Wood decomposing fungi also reside within their dens due to the high moisture content. Their urine and feces, in addition to the waste created by the other occupants of their den, fertilize the soils and create nutrient enriched areas. (Braun and Mares, 1989; Charles, et al., 2012; Whitford and Steinberger, 2010)

  • Ecosystem Impact
  • creates habitat
Commensal/Parasitic Species

Economic Importance for Humans: Positive

Woodrats are sometimes used as biological indicators to detect changes in habitat quality, particularly in Guadalupe Mountains National Park. Their population density is inversely related to the quality and quantity of the grassland. (Braun and Mares, 1989; Charles, et al., 2012)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Southern plains woodrats are potential vectors of a number of zoonotic illnesses. They are reservoir hosts of Leishmania mexicana, which can be transmitted to humans due to both species' interactions with sand flies. These animals may also be vectors for tularemia, plague, q fever, relapsing fever and Rocky Mountain spotted fever. Southern plains woodrats may also help spread chagas disease by hosting Trypanosoma cruzi, which infects both humans and other animals. (Charles, et al., 2012; Clarke, et al., 2013)

Conservation Status

This species is currently not considered endangered or threatened. According to the IUCN, southern plains woodrats have a stable population with a status of 'least concern' due to their wide distribution and large population size. Likewise, they have no specific listing by CITES. (Linzey, et al., 2008)

Contributors

Demetri Lafkas (author), Northern Michigan University, Leila Siciliano Martina (author, editor), Animal Diversity Web Staff, John Bruggink (editor), Northern Michigan University.

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

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.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

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.

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

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

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

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

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

vibrations

movements of a hard surface that are produced by animals as signals to others

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

Alligood, C., C. Wheaton, H. Forde, K. Smith, A. Daneault, R. Carlson, A. Savage. 2008. Pup development and maternal behavior in captive Key Largo woodrats (Neotoma floridana smalli). Zoo Biology, 27-5: 394-405.

August, P. 1978. Scent Communication in the Southern Plains Wood Rat, Neotoma micropus. American Midland Naturalist, 99/1: 206-218.

Braun, J., M. Mares. 1989. Neotoma micropus. Mammalian Species, 330: 1-9.

Charles, R., S. Kjos, A. Ellis, J. Dubey, B. Shock, M. Yabsley. 2012. Parasites and vector-borne pathogens of southern plains woodrats (Neotoma micropus) from southern Texas. Parasitology Research, 110: 1855-1862.

Clarke, C., K. Bradley, J. Wright, J. Glowicz. 2013. Case report: Emergence of autochthonous cutaneous Leishmaniasis in northeastern Texas and southeastern Oklahoma. American Journal of Tropical Medicine and Hygiene, 88-1: 157-161.

Conditt, S., D. Ribble. 1997. Social Organization of Neotoma micropus, the Southern Plains Woodrat. American Midland Naturalist, 137/2: 290-297.

Linzey, A., R. Timm, S. Alvarez-Castaneda, I. Castro-Arellano, T. Lacher. 2008. "Neotoma micropus" (On-line). IUCN Redlist of Threatened Species. Accessed August 29, 2013 at www.iucnredlist.org.

Pitts, R., J. Sharninghausen, H. Garner. 1985. A Note on the Extension of the Breeding Seasons of the Southern Plains Woodrat (Neotoma micropus Baird) and the Plains Pocket Gopher (Geomys bursarius Shaw) in Southcentral Texas. Bios, 56/2: 89-90.

Reid, F. 2006. Mammals of North America. Singapore: Houghton Mifflin Company.

Suchecki, J., D. Ruthven, C. Fulhorst, R. Bradley. 2004. Natural history of the southern plains woodrat Neotoma micropus (Rodentia: Muridae) from southern Texas. Texas Journal of Science, 56-2: 131-140.

Thies, M., W. Caire. 1991. Nearest-Neighbor Analysis of the Spatial Distribution of Houses of Neotoma micropus in Southwestern Oklahoma. The Southwestern Naturalist, 36/2: 233-237.

Whitford, W., Y. Steinberger. 2010. Pack rats (Neotoma spp.): Keystone ecological engineers?. Journal of Arid Environments, 74: 1450-1455.

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