The Response of Antelope Ground Squirrels (Ammospermophilus leucurus) to Human Impacts in the Western Mojave Desert

1998 ◽  
Vol 60 (1) ◽  
pp. 105-125
Author(s):  
Michael Starr
Keyword(s):  
Mojave Desert ◽  
Human Impacts ◽  
Ground Squirrels

scholarly journals Physiological and behavioral responses to anthropogenic stressors in a human-tolerant mammal

2019 ◽  
Vol 100 (6) ◽  
pp. 1928-1940 ◽  
Author(s):  
Talisin T Hammond ◽  
Minnie Vo ◽  
Clara T Burton ◽  
Lisa L Surber ◽  
Eileen A Lacey ◽  
...  
Keyword(s):  
Human Impacts ◽  
Ground Squirrels ◽  
Habitat Modification ◽  
Stress Physiology ◽  
Phenotypic Traits ◽  
Natural Habitats ◽  
Free Living ◽  
Anthropogenic Stressors ◽  
And Behavior ◽  
California Ground Squirrels

Abstract As humans continue to alter natural habitats, many wild animals are facing novel suites of environmental stimuli. These changes, including increased human–wildlife interactions, may exert sublethal impacts on wildlife such as alterations in stress physiology and behavior. California ground squirrels (Otospermophilus beecheyi) occur in human-modified as well as more pristine environments, where they face a variety of anthropogenic and naturally occurring threats. This makes this species a valuable model for examining the effects of diverse challenges on the physiology and behavior of free-living mammals. To explore potential sublethal effects of habitat modification on O. beecheyi, we compared body masses, behaviors, and fecal glucocorticoid metabolite (FGM) levels for free-living squirrels in human-disturbed versus undisturbed habitats. Prior to these analyses, we validated the use of FGMs in this species by exposing captive O. beecheyi to pharmacological and handling challenges; both challenges produced significant increases in FGMs in the study animals. While FGM responses were repeatable within captive individuals, responses by free-living animals were more variable, perhaps reflecting a greater range of life-history traits and environmental conditions within natural populations of squirrels. Animals from our human-disturbed study site had significantly higher FGMs, significantly lower body masses, and were significantly less behaviorally reactive to humans than those from our more pristine study site. Thus, despite frequent exposure of California ground squirrels to human impacts, anthropogenic stressors appear to influence stress physiology and other phenotypic traits in this species. These findings suggest that even human-tolerant mammalian species may experience important sublethal consequences due to human modifications of natural habitats.

Seasonal Water, Energy and Food Use by Free-Living, Arid-Habitat Mammals

1994 ◽  
Vol 42 (1) ◽  
pp. 55 ◽  
Author(s):  
KA Nagy
Keyword(s):  
Drinking Water ◽  
Mojave Desert ◽  
Dry Season ◽  
Ground Squirrels ◽  
Arid Ecosystems ◽  
Summer Drought ◽  
Kangaroo Rats ◽  
Adequate Food ◽  
Arid Habitat ◽  
Merriam's Kangaroo Rats

In arid ecosystems, the dry season is probably an especially challenging time for animals to find adequate food and water resources. Both stressful and benevolent times of the year can be identified by measuring rates of water and energy use (with doubly labelled water), diet and behaviour throughout a year in free-ranging animals. Such field studies have been completed on four species of arid-land mammals. Jackrabbits (Lepus californicus) are strict herbivores, and most Mojave Desert individuals have no access to drinking water, and depend on their food for their water. When vegetation dries up during the summer drought, most jackrabbits apparently die of dehydration and malnutrition, but populations are replenished by bountiful reproduction after winter rains. However, springbok antelope (Antidorcas marsupialis), also strict herbivores, can maintain water and energy balance throughout the year in the Kalahari in southern Africa by drinking water if available, but, if not, they obtain enough water from dietary plants, probably by feeding before dawn, when food items have taken up water from the humid air. Antelope ground squirrels (Ammospermophilus leucurus) are omnivorous in the Mojave Desert, and are active diurnally. They have lower water and energy requirements than non-desert mammals of the same body mass, like many desert mammals, but their ability to find succulent plant or animal foods in all seasons appears to be their primary survival tool. On the other hand, Merriam's kangaroo rats (Dipodomys merriami) are essentially nocturnal, and were thought to be strict granivores that never drank. A recent study, done throughout a year in the Mojave Desert, confirms their lack of drinking, but reveals that they eat much green vegetation in late winter and spring, probably in connection with reproduction. They obtain additional water throughout the year by caching dry seeds in humid burrows, where seeds take up water hygroscopically before being eaten. Although springbok, antelope ground squirrels and Merriam's kangaroo rats were in negative energy and water balance at times during the year, only jackrabbits were severely stressed by the dry season. Each species has a unique suite of desert survival mechanisms. Future research should include carnivores as well as arid-habitat marsupials.

Sign in / Sign up

Export Citation Format

Share Document