Saccostomus campestris

Geographic Range

Saccostomus campestris inhabits the savannahs, steppes, cultivated lands, scrub fields and sand plains of Angola, Botswana, Malawi, Mozambique, South Africa, Namibia, Tanzania, Zambia and Zimbabwe.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

Habitat

Saccostomus campestris prefers sandy, grassy or cultivated fields, steppe, and savannah habitats. The pouched mouse is completely terrestrial and lives in burrows that it either digs itself or finds vacated by other species.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune
• savanna or grassland savanna or grassland

Physical Description

Saccostomus campestris has a robust body (94-188 mm length, 40-85 g mass) with a short tail (30-81 mm). Their short legs and strong toes are well-adapted to digging. They have a broad head with short, rounded ears and small eyes. Pouched mice are named for their cheek pouches that stretch from the corners of their mouths to their shoulders that is used to carry seeds and grains. Female pouched mice have 10-12 mammae and both sexes have incisors that are not grooved. The rear feet of S. campestris are small, like many other members of the family Muridae .

The pelage of S. campestris is long, yet dense and fine. The coat is gray/gray-brown on top with lighter sides and white underparts (including the underside of the tail). S. campestris is sometimes said to resemble the common hamsters that are part of the U.S. pet trade.

Saccostomus campestris may be considered heterothermic due to its use of torpor to save energy when temperatures drop or when food resources become scarce. Scientists have observed that females employ torpor more often than males, presumably due to males' need to remain ready for reproductive opportunities that may arise.

Research indicates that males are not significantly heavier than females, on average, but older mice are heavier than younger mice. There is an annual cycle of body weights, such that on average, mice tend to be heavier in the wet season (December-March) than in the dry season (June-September), mainly due to an increased availability of high quality food resources. Much of the weight that is lost by a population of S. campestris is lost by younger mice, who tend to lose more weight during times of lowered food availability than older mice. This trend may be explained by the ability of the older, more experienced mice to find and secure more seeds in their burrows to be eaten throughout the winter than the younger mice.

• Other Physical Features
• endothermic endothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Female pouched mice tend to be aggressive toward all conspecifics except for a very short time, generally a 24-hour period that precedes their true estrous phase. Males must present themselves to females early in this pro-estrous stage or they will be in danger of injury or death from the aggressive females. The female’s estrous phase will commence approximately 12 hours after mating. If that mating did not result in a successful fertilization, the female will tolerate the presence of the male after a mating session. If the mating was successful in fertilizing the female, she will return to her normal aggressive behavior and injure the male if he does not leave within a few hours of copulation. This relationship of female aggression to successful conception is suspected to be influenced by hormones, as females are also intensely aggressive during pregnancy and lactation, but tests have been inconclusive thus far.

• Mating System
• polygynous polygynous

Saccostomus campestris completes its breeding in the wet season so that the young are born when food will be readily available to the lactating mother and emerging juveniles. The winter inhibition of reproduction in S. campestris seems to be associated with multiple environmental cues, including photoperiod, ambient temperature, and food quality and quantity. Given the set of environmental cues that will inhibit reproduction, mating in S. campestris is termed by some to be opportunistic based on the quality of the conditions presented by the environment. In the unpredictable environment of southern Africa, the male pouched mouse must be prepared for reproduction often and is therefore more reluctant to enter torpor than female conspecifics.

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

Mothers suckle their young in captivity for up to 8 weeks, during which time the young grow to be 38-56 g. The hoarding behavior of mothers also gives young that have not been fully weaned a good source of nutrition which allows them to leave the nest at a size that makes them more likely to survive.

In the wild, it is much more common that pups are weaned after 25 days. Gestation in the pouched mouse is less than 50 days. The young begin developing very rapidly after birth and are essentially pushed from the nest immediately after being weaned. The upper and lower incisors begin erupting anywhere from 10-14 days after birth and the eyes become fully functional around 24 days. The speed of growth in S. campestris is similar to that of house mice and brown rats.

Research in the laboratory has shown that if alien pups are introduced within the suckling period of her own pups, a female will accept the new pups as her own. If alien pups appear after her own pups have been weaned, however, the female will viciously attack the pups until they die. It has been postulated that the females cannot recognize their own young, but are sensing the difference in diet between weaned and non-weaned pups and can therefore distinguish alien pups which have been weaned. A female will not, however, attack one of her own pups if it has been eating solid food and suckling, indicating that the female must somehow detect a difference in those individuals that suckle and those that do not. All pups are moved from the nest at 25 days, regardless of whether or not they are the mother's own pups or alien pups. This study was undertaken in a laboratory environment, so while it appears that females will accept alien suckling pups as their own, it seems highly improbable that pups that have not yet been weaned would appear in a nursing mother's den outside of a laboratory environment.

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

Lifespan/Longevity

The lifespan of this specific mammal is not well-recorded, but due to its unpredictable environment, it may be expected to live only 1-3 years in the wild. This lifespan is similar to that of other small mammals in sub-Saharan Africa.

Behavior

Both sexes of S. campestris employ torpor as a way to lower metabolic needs when ambient temperatures drop or when food resources become less available. At temperatures of around 15-20 degrees Celsius, a pouched mouse may enter torpor. During torpor, a mouse that has been suffering from a poor diet may experience a body temperature as low as 15-20 degrees Celsius, but others can maintain a slightly warmer temperature. As stated above, male pouched mice tend to enter torpor much more reluctantly than females and this behavior is presumed to be related to a tradeoff males experience between reducing caloric needs in times of environmental stress and being prepared for sexual activity should the environment change. Because S. campestris males do not undergo a testes regression like most seasonally breeding mammals, they are presumably subject to higher testosterone levels year-round. These increased testosterone levels could be keeping males from entering torpor as frequently as the females, although more research is needed to definitely determine why males do not employ torpor very readily.

Saccostomus campestris is a solitary species that tends to live alone in a burrow with 2 entrance/exits and one large cavity that is used as a sleep/storage area. Each burrow is populated by more than one mouse only when a mother is suckling her pups. Once the pups are weaned at 25 days old, they are removed from the burrow. Due to its solitary nature, S. campestris is often aggressive toward conspecifics. Pouched mice will generally fill in the entrance/exit holes to their burrows when they are inside and have been observed to fill in the holes when out foraging as well, only to dig them back open upon their return. This behavior may be explained as protection from predators or food thieves or as a way to maintain higher temperatures in the burrow. The burrow ranges in size and complexity from a single roomed structure with less than 2000 mm of tunnels to a four-chambered structure with 8500 mm of tunnels. The burrows of pouched mice tend to contain very little bedding but do have large amounts of stored seeds and fecal material. Unlike some other rodents, S. campestris does not create a separate latrine area, so fecal material is scattered at random throughout the burrow. Aside from a storage place for seeds, the burrow also serves as a source of thermal protection for S. campestris , with summer temperatures around 30 degrees Celsius and winter temperatures around 20-25 degrees Celsius (when occupied). The burrow tends to be located at no greater than 600 mm into the soil and may either be dug by S. campestris itself or be recycled from a former user, such as a gerbil .

• Key Behaviors
• cursorial
• terricolous
• fossorial fossorial
• nocturnal nocturnal
• motile motile
• daily torpor
• solitary solitary
• territorial territorial

Home Range

Saccostomus campestris tends to stay close to the safety of its burrow, where it stores and eats much of its food. It is estimated that the mouse's foraging trips may take it anywhere from 200 m to 3.7 km from its burrow.

Communication and Perception

Saccostomus campestris is a nocturnal forager, therefore although it was not found in the literature, it is likely that pouched mice uses tactile and/or olfactory sensation to orient itself in the dark. Likewise, because S. campestris shows a preference for some types of food resources, it must use tactile and/or chemical signals to determine which food sources are the best.

Saccostomus campestris is a solitary animal and will defend its burrow and its solitary lifestyle by biting and physically attacking conspecifics. In this manner, it uses a tactile mode of communication to keep other mice away.

• Communication Channels
• tactile tactile

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

Food Habits

Saccostomus campestris is a granivore, primarily eating seeds, grains, and nuts. It also eats fruits, berries, insects such as ants or termites , and some leafy material. Pouched mice gets their name by gathering food in the field and carrying it to their burrows, where the food is eaten and/or stored. Foraging behavior takes place at night and in the more temperate areas of their range, pouched mice store food for the winter. If they are available, S. campestris prefers seeds of Acacia species, particularly A. tortilis . Their preference for these seeds may impact the community structure in years of either abundant Acacia production or high densities of mice. Studies also showed that when available, S. campestris hoards rat pellets, presumably due to their high protein levels and lower fiber content.

It appears that S. campestris , although it is fairly omnivorous, tends to hoard only seeds in its burrow, presumably because these are the least perishable constituents of its diet. Large caches, as are seen in the burrow of pouched mice living in the more temperate southern portions of their range, may represent up to 70 foraging trips. This value is based on the amount of seed found in the burrows and the maximum capacity of the cheek pouches of these mice. This caching may be essential in times when food becomes scarce. Caching may be particularly important for female pouched mice, as it may allow them to fuel the lactation process without leaving their young unattended as well as to provide their young with the increased nutrition that can help them to become large before they leave the safety of the nest.

• Primary Diet
• herbivore herbivore
  • granivore granivore

• Animal Foods
• insects

• Plant Foods
• seeds, grains, and nuts
• fruit

• Other Foods
• dung

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

Predation

While it is presumed that S. campestris faces predation from larger carnivorous mammals and snakes , the only predator that has been specifically noted for this species is the barn owl .

One explanation for the tendency of S. campestris to seal off the entrances to its burrow while it is inside is protection from predators, although it is equally likely that the pouched mouse seals itself in to maintain thermal protection or hide its cache from other terrestrial seed eaters.

Ecosystem Roles

Due to its preference for specific types of seeds, S. campestris can impact the structure of the vegetation in its ecosystem by consuming large numbers of those preferred seeds. One of those preferred seeds is Acacia tortilis , which is heavily predated by S. campestris and other small mammals when it is available. Additionally, S. campestris impacts its environment by indirectly competing with other small mammal seed eaters, such as Mastomys natalensis , Aethomys chrysophilus , Acomys spinosissimus and Tatera leucogaster .

Pouched mice are burrowers, therefore they provide habitat for other small mammals and aerate the soil. Likewise, if any seed that is cached is not consumed, it has a better chance at germinating and surviving than seeds that are left on the surface that will likely be consumed by another small mammal or be dessicated before germination.

• Ecosystem Impact
• disperses seeds
• creates habitat
• soil aeration soil aeration

Economic Importance for Humans: Positive

Pouched mice are sometimes sold as a pets, although their aggressiveness toward conspecifics would require that they only be caged individually. In some areas, they are a food source for humans, as each mouse provides 723 KJ of energy when consumed.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

Saccostomus campestris can be a crop pest for grain farmers and it is a host for a number of pulicid fleas .

• Negative Impacts
• crop pest

Conservation Status

This species is not considered to be threatened.

Other Comments

Recent research indicates that S. campestris and S. mearnsi , the only other member of this genus, are still actively speciating and that the classifications that we have made thus far may need to be revised as more evidence of this speciation becomes available.

Additional Links

Encyclopedia of Life

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

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

References

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Ellison, G., G. Bronner, P. Taylor. 1993. Is the annual cycle in body weight of pouched mice ( Saccostomus campestris ) the result of seasonal changes in adult size or population structure?. Journal of Zoology , Vol. 229: 545-551.

Ellison, G. 1993. Group size, burrow structure and hoarding activity of pouched mice ( Saccostomus campestris : Cricetidae) in southern Africa. African Journal of Ecology , Vol. 31: 135-155.

Ellison, G. 1995. Is Nest Building an Important Component of Thermoregulatory Behaviour in the Pouched Mouse ( Saccostomus campestris )?. Physiology & Behavior , Vol. 57, No. 4: 693-697.

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