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Food and Predation

Food

Kangaroo rats are predominately granivorous (Morgan et al. 1992) however they will occasionally eat vegetatative parts of plants and at certain times of the year they will even eat some insects (Howard 1994). Heteromyids, including kangaroo rats, are especially adept at harvesting dispersed seeds that are unpredictable and seasonal in nature in mixed soils (Morgan et al. 1992). The different seed types of mesquite, creosote, bush, purslane, ocotillo, and grama grass have been frequently found in their cheek pouches ( Bouskila 1995). Food is an important factor which effects kangaroo rats because in Heteromyids the per capita population growth rate is a function of food availability ( Morgan et al. 1992) because the kangaroo rat will only reproduce if food sources are plentiful.

Kangaroo rats will store seeds in excess of their immediate need in seed caches ( Reynolds 1958) and will wait until they are safely at these caches (Merriam) or in their burrows ( Banner-tail) to eat the seeds (Morgan 1992). The caching behavior of kangaroo rats can cause a large impact on the rangeland and croplands in which kangaroo rats live ( Howard 1994) because of its affect on the distribution and abundance of plants ( Jenkins et al. 1995). The Merriam kangaroo rat is unique in that it has structural, behavioral and physiological adaptations ( Lidiker 1960) does not require water to survive for extended periods of time (Smithsonian Institue Press 1999). Because of this adaption, however, the Merriam kangaroo rat is very dependant on an abundant food supply. This adaptation may be why Merriam kangaroo rats are said to be the most successful species of kangaroo rat in desert environments ( Lidicker 1960).

picture of mesquite dune whe kangaroo rats will often cache curtesy of Kerry S. Kilburn Ph.D: link to picture

Although, the availability of seeds of the kangaroo rat vary by season and location, I would define them as an abundant resource for the kangaroo rat.

Predation

The predators of the kangaroo rat are the coyote, fox, badger, owl, snake (Western Rattlesnake, Gopher, and King) and weasel (Smithsonian Institute Press 1999; California EPA Department of Pesticide Protection 2002). They are also subject to external parasites, lice, ticks, and fleas ( Texas Tech University 1997 ). Kangaroo rats share their habitat with Antelope, Jackrabbits, Squirrels and Pocket Mice ( Smitsonian Institute Press 1999). While predation seems to have been a defining force in the kangaroo rats behavioral and physiological adaptations, it seems to be an unimportant factor now in limiting kangaroo rat numbers. This could be because most predators of the Kangaroo rat also have a varied diet so they are not solely dependant on catching kangaroo rats as a food source ( Reynolds 1958) as well as the fact that kangaroo rat behavior is highly adapted to avoid predators. Research seems to lead to the conclusion that predation seems to have been the strongest adaptative force for the kangaroo rat( Thompson 1982).

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