|Longland, William - Bill|
Submitted to: Journal of Mammalogy
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/24/2005
Publication Date: 6/15/2006
Citation: Murray, A.L., Barber, A.M., Jenkins, S.H., Longland, W.S. 2006. Competitive environment affects food hoarding behavior of Merriam’s kangaroo rats (Dipodomys merriami). Journal of Mammalogy. 87:571-578. Interpretive Summary: The Merriam’s kangaroo rat is a seed-eating desert rodent that plays an important role in the biology of arid rangeland plant species through both its consumption of large quantities of seeds and it’s habit of caching seeds just under the soil surface, where they may germinate and establish new plants. This type of seed caching, called scatter hoarding, tends to benefit native arid land plants, many of which provide important forage for livestock and wildlife, but reduce the survival of various weeds that germinate from rodent caches. An alternate way of caching seeds, larder hoarding (the placement of large numbers of seeds in a den or burrow) generally does not allow seeds of any plant species to germinate, and therefore scatter hoarding is far more beneficial to rangelands. We investigated how the presence of other related species may influence the degree to which Merriam’s kangaroo rats use one or the other of these alternate caching behaviors. When neighbors were predominantly other Merriam’s kangaroo rats, these animals tended to scatter hoard seeds more (i.e., larder hoard less) than when neighbors of other rodent species were common. Thus, the beneficial effects of these kangaroo rats on desert plants are partly influenced by whether they share their habitat mainly with members of their own or of other species.
Technical Abstract: North American desert rodents in the family Heteromyidae live in an unpredictable environment characterized by extremes in temperature and food availability; therefore, the ability to hoard food is a vital adaptation. Although much laboratory research has investigated the food hoarding tactics of heteromyid rodents, data from natural systems are scarce. We used a combination of fluorescently labeled seeds and observations of focal individuals to evaluate food hoarding behavior in wild Merriam’s kangaroo rats (Dipodomys merriami) living in different competitive environments. There was considerable individual variation within populations in the tendency to larderhoard seeds in a burrow versus scatterhoard seeds in widely dispersed locations. However, individuals living in a system where competitors are predominately conspecific scatterhoarded more than those living in a system where conspecifics were less abundant and heterospecific competitors were also present. Also, pilferage was more common between Merriam’s kangaroo rats than across species. Comparisons of food hoarding between communities with different species composition indicate that intraspecific variation in behavior may be associated with variation in competitive environments.