Pappogeomys bulleri

Geographic Range

All nine subspecies of Pappogeomys bulleri are found in western central Mexico, in the states of Nayarit, Jalisco, Colima, and Michoacan.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Pappogyomys bulleri is a montane species that prefers soils of volcanic origin. It lives at sea level, extending into elevations as high as 3,050 m. It inhabits Jalisco, Mexico, which is well known for a variety of terrains and climates. In Jalisco, seasons are based on rainfall, with 80% of rain coming between July and October. The average monthly temperature in this region is 24.9C. Pine-Oak forests border meadows and agricultural zones. Tropical deciduous forests are also found in the region. Subspecies of P. bulleri are found in all the terrains and climates in the area.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• scrub forest scrub forest
• mountains mountains

• Other Habitat Features
• agricultural agricultural

Physical Description

The morphology of Pappogeomys bulleri is well adapted to fossorial life. They have small, flattened heads, short necks, and short, broad, and muscular forelimbs. The eyes, nose, and ears can be closed by flaps of skin to keep out dirt when digging. Their lips can close behind their incisors, allowing them to dig with their teeth and keep their mouth free of dirt. Their common name, Buller's pocket gopher, refers to the fur-lined cheek pouches in their mouths. They use these pouches to transport food from above ground into their burrows. They have large, sharp claws on their forelimbs and shorter claws on their hind feet.

The pelage varies by subspecies, but is generally pale to dark grey basally and tawny to cinnamon brown dorsally. Long, soft and fine, their fur lies near the body and falls in one direction. They sometimes have a white or buff nasal patch, although it is often missing. Their tails are naked and white, extending a distance less than half the length of the body and head. Pappogeomys bulleri is sexually dimorphic with males larger than females, but this difference is not as pronounced as in other gopher species ( Geomyidae ). Variation in size also exists among subspecies. On average, the total body length of males is 214 to 237 mm and the total body length of females is 130 to 175 mm. Males continue to grow in body size throughout their lifetime, while females stop growing at sexual maturation. Average measurements are as follows (in mm): length of head and body 130-175; length of tail 50-85; length of ear 6.5-8; length of hind food 28-35; occipitonasal length 36.2-44.0; zygomatic breadth 21.4-27.8; width across squamosals 20.3-27.2; breadth of interorbital constriction 6.5-8; length of nasals 11.8-16.2; length of maxillary toothrow 7.5-10.2; width of upper incisors at cutting edge 3.8-4.9; length of rostrum 16.6-21.4. Overall, the skull of P. bulleri is small and narrow.

The teeth are similar to those of other rodents and gophers. They have two large, central incisors that they use in digging. These incisors have a single, medial sulcus that runs down the entire labial surface of the tooth. Like those of other rodents, the incisors are continually worn down and regenerated. Lower incisors are regenerated significantly faster than upper incisors. The first molar has a thin enamel plate that extends across the posterior wall of the tooth and is variable among subspecies. Pocket gophers have 20 teeth total, with the dental formula: i 1/1, c 0/0, p 1/1, m 3/3.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Pappogeomys bulleri is thought to have a polygynous mating system. The range of one male overlaps with those of several females but ranges of the females do not overlap. Other than interacting while mating, individuals remain solitary.

• Mating System
• polygynous polygynous

The mating season for P. bulleri is year round, with the most active period being between late winter and early summer. Mating behavior and breeding activity begins at about nine months to one year of age for both sexes. Females are sexually mature once their pubic symphysis has opened, widening the birthing canal. After the first breeding season, the pubic symphysis is completely absorbed at the command of relaxin, an ovarian hormone. Males are sexually mature when the baculum and sex glands are fully developed.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Female P. bulleri have six mammae: one pectoral pair and two lingual pairs. A female will have anywhere from 2 to 11 young in a litter. The gestation period is around 20 days. Newborn Buller's pocket gophers are altricial. On average, they weigh between 2.5 and 4 g, with cheek pouches not fully developed and eyes that are still under a thin layer of skin. In about one month, their cheek pouches, eyes and ears are opened and one week later they are able to use their cheek pouches to carry food. After two months, siblings begin to fight with one another, undergo weaning, and disperse soon afterwards. Juveniles molt to show adult pelage when they are near 100 days old.

• Parental Investment
• altricial altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

The maximum lifespan of pocket gophers is 5 years. The average age of individuals found in collections is 13.6 months for males and 18.6 months for females. The oldest males trapped in the wild were 4 and 5 years old, and the oldest females trapped were 4 years and 9 months.

Behavior

Pappogeomys bulleri is highly fossorial and lives primarily in complex subterranean tunnel systems. Like other fossorial rodents, P. bulleri uses a combination of claws and incisors to help dig burrows. The burrows are dug with the animal’s entire body, and their diameter depends on the size of the individual. When digging, the gopher loosens dirt with its claws and incisors, then pushes the dirt underneath its body. The gopher then turns around and pushes the dirt to the surface. As it is digging, it uses its incisors to clip roots in the path of the burrow and its large claws to remove small rocks. Depths of the burrow system ranges from 10 to 30 cm underground and side tunnels are frequently found branched off of the main tunnel. Side tunnels are used as a place to store food. Nesting and breeding burrows are dug deeper than the main system, and the gopher lines these with dried grasses. Pocket gopher tunnel systems are closed and thus are fairly resistant to rain and flooding. Gophers open their tunnels several times per day to leave them to gather food or excavate soil, but close them again with a small mound of loosened soil deposited in a fan-shape of concentric rings.

Pappogeomys bulleri is primarily solitary, living in close proximity to other members of the species only during periods of mating or while raising young. The species is active year round and can be quite aggressive to conspecifics when they encroach on another’s territory. Although P. bulleri is territorial, they are docile rodents in most situations, particularly when interacting with people. Pocket gophers are active all day, rotating between active periods and resting periods. Active periods last about 36 minutes and resting periods are about an hour. They have been observed to have 16.1 activity periods a day.

• Key Behaviors
• fossorial fossorial
• diurnal diurnal
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary
• territorial territorial

Home Range

The home ranges of P. bulleri are similar to those of other pocket gophers. Males generally have larger home ranges than females. Individuals that live closer to or under agricultural areas tend to have smaller home ranges than individuals in less developed areas.

Communication and Perception

Pappogeomys bulleri perceives its environment primarily through sound, touch, and smell. Gophers have vibrissae around their face and wrists which aid in navigating in burrows. The ears of P. bulleri are unique when compared with other rodents. The bullae are comprised of very thick bone and show modifications in the stapes. These features are in response to their subterranean lifestyle. They do not have sensitive hearing systems for low or high frequencies, which may protect their ears from incessant underground background noises.

Pappogeomys bulleri communicates with conspecifics vocally. When confronted with each other, two P. bulleri will hiss or click their teeth at each other. In captivity they are known to squeal when angry or in pain.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Buller's pocket gophers are strictly herbivorous and eat a variety of plant foods. They prefer forbs, comprising 40% of their diet, but also eat grasses (30% of their diet) and the roots of xerophytic shrubs. They gather most food above ground, and transport it into their burrows by means of cheek pockets. Once underground, the food is either eaten or stored in sealed compartments. Occasionally, P. bulleri eats roots from inside of the burrows. Water is mainly obtained through food in the diet.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Pappogeomy bulleri is most susceptible to predation while above ground. Pocket gophers are important prey for a variety of predators, including weasels, coyotes, birds of prey, foxes, bobcats, domestic cats, snakes, and skunks. Although snakes will live in the burrows of P. bulleri , they are physically unable to kill them while underground due to space restrictions. Avian predation has the most impact on populations of pocket gophers, but studies have found that the main selective pressures on population size are food and habitat availability, not predation.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Pappogeomys bulleri is important to the ecosystem in many ways. Their constant digging and burrowing work to aerate soils, slow runoff, and fertilize soils. These activities enrich the soil and increase yield of the plants the gophers like to eat. The burrows of the gophers become a habitat to other organisms as well. Reptiles, other mammals (moles, squirrels, mice, rats, voles, and weasels), and some birds benefit from their burrow systems. These pocket gophers play an important role in the ecosystem as a host for parasites, including chewing lice, fleas, mites, and ticks. Other ways in which they affect their environment are as an important prey species (see section above) and as herbivores. Large populations of pocket gophers can change plant composition in an area: their mixing of soils causes foods that pocket gophers prefer to eat increase in quantity, while the plants they choose not to eat are no longer as common.

• Ecosystem Impact
• creates habitat
• soil aeration soil aeration

Economic Importance for Humans: Positive

Pappogeomys bulleri populations have a positive impact on soil fertilization and plant growth, and may help promote good soils for agriculture.

Economic Importance for Humans: Negative

Pappogeomys bulleri are serious agricultural pests. They are known to gnaw through plastic irrigation pipes and electric cables and eat a significant portion of crops or food designated for livestock or humans. Studies have shown that gophers can reduce the foliage intended for livestock by twenty percent. Farmers in areas with high populations of gophers have developed a number of ways to deal with gophers. Poisons are lowered into the gophers burrow systems or gophers are baited and caught. Gophers are very efficient diggers, however, and are able to counter many of these strategies. Within the range of P. bulleri , many villages have a “tucero,” a person whose job it is to trap and kill gophers. This job is passed from father to son and the tucero is a respected member of the community.

• Negative Impacts
• crop pest

Conservation Status

Pappogeomys bulleri populations are currently stable.

Additional Links

Encyclopedia of Life

Contributors

Emily Kenny (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

References

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