Animal Diversity Web

Geographic Range

The range of big-eared woodrats (Neotoma macrotis) extends from parts of California into Mexico. They are found as far north as Salinas Valley in California and as far south as Baja California, Mexico. They are also in most parts of southern California between these two points, as well as in the southern portions of the Sierra Nevada and Coastal Ranges. (Haynie, et al., 2007; Matocq and Murphy, 2007)

• Biogeographic Regions
• nearctic
  • native

Habitat

Big-eared woodrats are abundant in areas densely populated with trees, specifically coast live oaks, but also California foothill pines. Although they are more common in wooded areas, they are also found along rivers in their native range. Chaparral and coastal areas of California and Baja California are also preferred habitats of this woodrat. They are also more abundant in the presence of certain types of understory plants including Pacific poison oaks, toyons, and California buckthorns. There are no specified altitude ranges for this species; however, big-eared woodrats live in and around the Sierra Nevada mountain range, although they are found mainly in the foothills. (Haynie, et al., 2007; Matocq and Murphy, 2007; Skopec, et al., 2008)

• Habitat Regions
• temperate

• Terrestrial Biomes
• chaparral
• forest
• scrub forest

• Other Habitat Features
• riparian

Physical Description

The fur of big-eared woodrats can range from light to dark brown with shades of gray. They are distinguished from their sister species primarily based on the morphology of certain parts of their skull, but also on the morphology of the mature male's genital. The sizes of certain parts of their skull are also indicative of the species. The most distinctive of these cranial features are the zygomatic (width), the rostrum (width and depth), the interptyregoid fossa (width), and the tympanic bulla (length). Compared to their more northern and inland sister species, big-eared woodrats have smaller relative dimensions of these cranial features on average. Other diagnostic cranial features that can be used are the size of the vomer, and the size of the presphenoid bone compared to the basisphenoid. One of the two forms of big-eared woodrats' glans penis serves as a diagnostic tool that can be used when dealing with male woodrats. The diagnostic form is described as "flower-like", with a long skinny projection emanating from the tip. The other form, which is most common among Neotoma species is shorter and more oblong. The average female body length is 183.9 mm ± 2.8, while the average body length for males is 193.8 mm ± 3.1. The mean mass of big-eared woodrats is 204 g ± 13.6. Infant woodrats lack hair when they are born, although they do already have their whiskers (known as vibrissae). Healthy pups weigh anywhere from 12 to 14 grams. Their dorsal body parts start to darken after a couple days, with hair starting to grow after a couple weeks. The pups show control of their movements before they can open their eyes, which occurs around the thirteenth to fourteenth day post-birth, plus or minus two days. (Haley, et al., 2007; Matocq and Murphy, 2007; Matocq, 2002; Wood, 1935)

• Other Physical Features
• endothermic
• bilateral symmetry

• Sexual Dimorphism
• male larger

• Range mass

  190.4 to 217.6 g

  6.71 to 7.67 oz

• Range length

  181.1 to 196.9 mm

  7.13 to 7.75 in

• Average length

  188.1 mm

  7.41 in

Reproduction

There are reports that big-eared woodrats do have characteristic mating rituals, though these have not been experimentally demonstrated. This involves sniffing by both sexes and ultimately presentation of the vagina by the female. This species can be very aggressive. In attempts to breed pairs of woodrats in the lab, fighting ensues, resulting in serious damage to one sex or the other, or both, and even some fatalities. Predictions that this type of behavior is carried out in the wild were supported upon examination of captured individuals with scars and other bodily markings, indicative of fighting with members of the same or very similar species. In regards to mannerisms and pre-intercourse behaviors, both male and female woodrats can initiate interest in the opposite sex by circling, sniffing, and licking the potential mate, especially around the genitals. Signs of fighting can occur, with the woodrats standing on their hind limbs and leaning against one another supported by their forelimbs, though this is not always predictive of an unsuccessful mating attempt. Ultimately, if the pre-intercourse rituals are successful, no matter who initiated the advancement, receptiveness of the female is displayed by her remaining immobile and raising her hind end. Males have reportedly copulated up to eight times in a ten minute period, with each successful attempt taking an average of five seconds to complete. It is the males who appear to dictate when no more reproduction will take place, as they isolate themselves from the females. In captivity, this species does not carry out reproductive events all that well, nor are fertility rates very high. Males tend to mate with more than one female successfully, suggestive of a polygynous system. (Haynie, et al., 2007; Matocq and Lacey, 2003; Matocq, 2004; Wood, 1935)

• Mating System
• polygynous

The breeding season of big-eared woodrats is February to September, even though there are accounts of birthing events outside of these months, with a maximum difference of two months. Male testes grow during the mating season and shrink back down after the season comes to a close. A membrane closes the vaginal orifice in young females. This membrane is easy to break and disappears as woodrats age, in correlation with the onset of the mating season. Males likely reach sexual maturity as soon as their testicles grow and females reach sexual maturity as their vaginal membrane disappears. However, young woodrats in their first mating season display mature characteristics but have reportedly failed to carry out reproduction successfully. This may mean there are additional temporal factors associated with reaching sexual maturity, and that maturity is not based on morphological changes of genitalia alone. Male spermatozoa have been characterized as long and slender, with a defined hook-like head. Several studies have shown the inner lining of the vaginal walls contain various proportions of epithelial cells, cornified cells, and leukocytes, with either of the last two being most prominent. It takes an average of 33 days for woodrats to develop and undergo live birth, the female's four mammae start to swell and lactate at this time. Groups of kin have been born with a maximum of three individuals at a time. (Matocq and Lacey, 2003; Matocq, 2004)

• Key Reproductive Features
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• viviparous

• Breeding interval

  Male big-eared woodrats can breed multiple times throughout the breeding season, while females generally only breed about 3 times within the same time span.

• Breeding season

  Big-eared woodrats breed from February to September.

• Range number of offspring

  2 to 3

• Average gestation period

  33 days

Mothers tend to provide more care for the offspring than fathers. This care includes allowing suckling for nourishment. There have been relatively frequent incidents in which mothers have simply ignored, chosen to abandon, and even eaten their offspring. Mothers who give birth in the laboratory demonstrate some level of protectiveness over their offspring; they are feisty when their young are approached and they relocate their offspring by biting them on their neck or shoulder to move them to a safer position relative to the researchers. Fathers show varying patterns of parental investment. Some stay and aid the mother in rearing their offspring, although there are no documented reports of fathers staying to watch their offspring reach maturity. (Wood, 1935)

• Parental Investment
• female parental care
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

There is currently very little information available regarding the lifespan of big-eared woodrats. One current estimate suggests that these woodrats have an approximate lifespan of about 1.6 years. However, other species from this genus have a much longer estimated lifespan. For instance, white-throated woodrats have an estimated captive lifespan of 9.5 years, eastern woodrats have an estimated captive lifespan of 8.6 years, and desert woodrats have an estimated captive lifespan of 10.5 years. (Matocq, 2004; Tacutu, et al., 2013)

Behavior

Big-eared woodrats are nocturnal. One of their most interesting social behaviors is the construction of "houses" or dens from left over shrubs, sticks, and plant material. Hollow logs can serve as alternate houses/dens. Dens likely play a role in establishing philopatry and kinship among females. Males do not behave as consistently as females. Males remain in the same area for given amount of time, before or after mating, and are not as strongly associated to any one individual house as females are, although they often help build them. There is also research that suggests dens serve as a means to establish territoriality and only certain, related individuals are allowed to enter them. Some dens may have survived for as long as 60 years and may be "passed" down to female offspring. Just under a quarter of all sampled neighboring houses were inhabited by closely related species and just over half return and live either in the house where their mother lived or in a neighboring one. This suggests that although some females may be philopatric, it is not the case for the entire population. (Matocq and Lacey, 2003; Wood, 1935)

• Key Behaviors
• terricolous
• nocturnal
• motile

• Range territory size

  159.8 to 204.0 m^2

Home Range

Females studied for philopatry consistently return to their den after being captured and released. One study found females spend the vast majority of their time within 100 m of their dens. Their average home range is about 181.9 m^2 ± 22.1, with houses every 7.5 m ± 0.6. (Matocq and Lacey, 2003)

Communication and Perception

Large-eared woodrats use their visual perception to navigate in the environment and to establish a relative distance from conspecifics and other species. The behaviors concerning reproductive success involve close proximity and contact, either aggressive or non-aggressive. When going through heat, females release pheromones that excite males in the area. Although kin groups are not as stable as in other species, related female big-eared woodrats might be at an advantage in society as a result of cooperation and effective communication. (Matocq and Lacey, 2003; Wood, 1935)

• Communication Channels
• visual
• tactile

• Other Communication Modes
• pheromones

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Big-eared woodrats are dietary specialists. In the wild, their diet is composed of more than 80% tree bark and foliage from coast live oaks. Consuming, degrading, and digesting this type of food is not easy, even for a general herbivore due to the incredibly high phenolic and tannin contents. However, big-eared woodrats have an adapted metabolism that allows them to degrade phenolic compounds to a significant extent, especially tannins. Key adaptations are salivary enzymes in the mouth and secretions and bacteria throughout the gut that enhance digestion of plant matter and absorption of nutrients. Big-eared woodrats also have a marked ability to digest nitrogen-containing compounds as well as fiber. When big-eared woodrats are in a region that overlaps with one of their sister species, such as dusky-footed woodrats or desert woodrats, they continue to eat what they usually do, while the sister species modifies their eating habits to accommodate them, even though all of the species primarily eat oak leaves. This example of habitat partitioning further stresses just how much of a specialist eater big-eared woodrats are and indicates they are better competitors compared to the other species. Interestingly, compared to relatives on a non-tannin diet, big-eared woodrats have much smaller livers. (Haley, et al., 2007; Matocq and Murphy, 2007; Matocq, 2004; Skopec, et al., 2008)

• Primary Diet
• herbivore
  • lignivore

• Plant Foods
• leaves
• wood, bark, or stems

Predation

Known predators of big-eared woodrats include northern spotted owls, as well as local snake species and birds of prey. Their best anti-predatory defense against avian predators is to seek refuge in their dens. (Haynie, et al., 2007)

• Known Predators

  • northern spotted owls (Strix occidentalis caurina)

Ecosystem Roles

Big-eared woodrats act as reservoir hosts for a few human pathogens. These arenaviruses include Borrelia burgdorferi, Ehrlichia phagocytophila, and Yersinia pestis, which cause Lyme disease, human granulocytic ehrlichiosis, and the plague, respectively. Furthermore, northern spotted owls are considered an endangered species and one of their main prey items are big-eared woodrats. Thus destruction of big-eared woodrats' habitat could lead to an even greater decline in the owl's numbers, or potentially to their extinction. (Haynie, et al., 2007)

Economic Importance for Humans: Positive

There are no documented ways in which big-eared woodrats benefit humans economically.

Economic Importance for Humans: Negative

Big-eared woodrats are known hosts and transporters of viruses that infect humans. (Haynie, et al., 2007)

• Negative Impacts
• injures humans
  • carries human disease

Conservation Status

Though the species is not endangered, there is concern over habitat destruction, especially in chaparral areas due to anthropogenic developments and disruptions. Examples of the disruptions include mining and agriculture. (Skopec, et al., 2008)

• IUCN Red List

  Least Concern

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Comments

This species has several common names, which include big-eared woodrats, large-eared woodrats, and San Diego woodrats. Big-eared woodrats were confirmed as a new species of genus Neotoma after Matocq provided evidence in 2002 that they have enough morphological and genetic differences to be separate from the previous, more encompassing group, Neotoma fuscipes. Neotoma fuscipes is now considered a sister species to Neotoma macrotis. (Matocq, 2002)

Contributors

Tim Saltys (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

References

Haley, S., J. Lamb, M. Franklin, J. Constance, M. Dearing. 2007. Xenobiotic Metabolism of Plant Secondary Compounds in Oak (Quercus agrifolia) by Specialist and Generalist Woodrat Herbivores, Genus Neotoma. Journal of Chemical Ecology, 33/11: 2111-2122.

Haynie, M., C. Fulhorst, M. Rood, S. Bennett, B. Hess, R. Bradley. 2007. Genetic Variation in Multilocus Microsatellite Genotypes in Two Species of Woodrats (Neotoma macrotis and N. fuscipes) from California. Journal of Mammalogy, 88/3: 745-758.

Matocq, M. 2002. Morphological and Molecular Analysis of a Contact Zone in the Neotoma fuscipes Species Complex. Journal of Mammalogy, 83/3: 866-883.

Matocq, M. 2004. Reproductive Success and Effective Population Size in Woodrats (Neotoma macrotis). Molecular Ecology, 13/6: 1635-1642.

Matocq, M., E. Lacey. 2003. Philopatry, Kin Clusters, and Genetic Relatedness in a Population of Woodrats (Neotoma macrotis). Behavioral Ecology, 15/4: 647-653.

Matocq, M., P. Murphy. 2007. Fine-Scale Phenotypic Change Across a Species Transition Zone in the Genus Neotoma: Disentangling Independent Evolution from Phylogenetic History. Evolution, 61/11: 2544-2557.

Skopec, M., S. Haley, A. Torregrossa, M. Dearing. 2008. An Oak (Quercus agrifolia) Specialist (Neotoma macrotis) and a Sympatric Generalist (Neotoma lepida) Show Similar Intakes and Digestibilities of Oak. Physiological and Biochemical Zoology, 81/4: 426-433.

Tacutu, R., T. Craig, A. Budovsky, D. Wuttke, G. Lehmann, D. Taranukha, J. Costa, V. Fraifeld, J. de Magalhaes. 2013. Human Ageing Genomic Resources: Integrated databases and tools for the biology and genetics of ageing. Nucleic Acids Research, 41(D1): D1027-D1033. Accessed July 30, 2014 at http://genomics.senescence.info/species/browser.php?type=5&name=Neotoma.

Wood, F. 1935. Notes on the Breeding Behavior and Fertility of Neotoma fuscipes macrotis in Captivity. Journal of Mammalogy, 16/2: 105-109.