San Joaquin Antelope Squirrel
The San Joaquin antelope squirrel, also known as Nelson’s antelope squirrel, is native to the San Joaquin Valley in California. This squirrel lives on slopes and ridge tops, inhabiting the western edge of the valley. The range of the San Joaquin antelope squirrel has grown smaller, resulting in its status of endangered. The original habitat of this antelope squirrel, Carrizo Plain, is where most of the squirrels reside now. The burrows of these squirrels can be found in separate areas in Kern Counties and San Luis Obispo. The San Joaquin antelope squirrel favors rich, deep soil to easily dig for food in summer or winter. Instead of digging its own burrow, however, it will claim abandoned kangaroo rat homes.
The San Joaquin antelope squirrel resembles other antelope squirrels, with its yellowish fur and white belly. It has white streaks on the sides of its body, with a black edged tail. Adult males can be up to 9.8 inches in length, with the females reaching an approximate size of 9.4 inches in length. Being social creatures, the San Joaquin antelope squirrels will live in small colonies of up to eight familial individuals.
After carefully assessing the area around a burrow, a San Joaquin antelope squirrel will follow a particular route to forage for food, escaping back into the burrow when necessary. It does not use a lot of energy throughout the day, in order to avoid dangerous heat levels. A temperature of 87 degrees to 89 degrees Fahrenheit can kill this squirrel, so it prefers to search for food in the mornings and the evenings; however, it does not usually appear before sunrise. After returning to their burrows at around noon, the squirrels will remain there through the afternoon. They may re-emerge as early as two o’ clock PM in order to continue searching for food. On a good day, the squirrel will take its time, barely taking interest in food it does not like. If the weather is extremely hot or cold, it will quickly gather as much food as possible. In order to avoid predators, it will use an alarm call that is quiet and coupled with convulsive movements to let its family know that danger is near. It will also use the white underside of its tail to mimic a plant called thistledown blowing in the wind, as a camouflage against its predators. Horned larks and white crowned sparrow are two birds that the squirrel will listen to for alarm calls, as another means of watching for danger. With these methods, along with quick movements, the San Joaquin antelope squirrel can avoid its predators, which include badgers and coyotes.
The San Joaquin antelope squirrel is omnivorous, consuming green vegetation, seeds, insects, and even dried animal material. This squirrel rarely stores food, and its diet depends on the season or time of day. Redstem fialree and brome grass are two main components of its diet. During mid-April to December, the San Joaquin antelope squirrel will eat mainly insects, because they are most common during that period. From December to mid-April, it will eat mainly green vegetation because it is more abundant. Seeds are not a likely meal for this antelope squirrel, even when insects or green vegetation are less present, but it will eat them if necessary. It is thought that they do not prefer seeds because the water content in them is lower than that of vegetation and insects. A water source is not readily available, so they must digest moisture from the food they eat. In a laboratory study, the squirrels accepted water, but they are able to go seven months in the shade without it.
Breeding in late winter to early spring, the San Joaquin antelope squirrel will produce most of their young in March. Baby antelope squirrels do not emerge from the nest until about the first week in April. Timing is important to the squirrels, as green vegetation only grows for a certain amount of time. When weaning, a mother squirrel will eat alone and ignore her babies’ attempts to nurse, and may even sleep in a different den if deemed necessary. It is thought that the weaning process is completed before the young even leave the burrow. They can be seen foraging for food on their own once they do. Reaching adulthood by summer, the pelt of the San Joaquin antelope squirrel is apparent. It is difficult to determine the age of these squirrels because most do not live past a year, although some have lived up to four years in the wild.
Urban development and an increase in agriculture in the San Joaquin valley have proved to damage the antelope squirrel population. The squirrels will not live on cultivated lands, and so their habitat range is limited; invasive plants are also causing antelope squirrels to lose their natural territories. Pesticide drift from nearby fields can harm the squirrels as well. Not only are these problems affecting the squirrels, but they are also endangering a number of plant species and other native creatures in the valley.
Efforts to save the San Joaquin antelope squirrel are being made, although most have proved to be either too expensive or too dangerous for plant life and other species in the area. Attempts at burning invasive plants could potentially burn native species as well, and herbicides are a danger in high winds to San Joaquin creatures. Mechanical and chemical methods are too expensive and time consuming to utilize in conserving the antelope squirrels. In order to determine a conservation method that can save the squirrels, private landowners and the U.S. Fish and Wildlife Service would need to create a plan that would include the preservation and conservation of many native San Joaquin species of plants and animals, without harming the farmers’ way of life. A recovery plan dated to 1998 was created by the USFWS that holds an idea that the Safe Harbor Agreements under section 10 of the Endangered Species Act could aid in the efforts to save the squirrels, but more research is needed before any plan of conserving and restoring the San Joaquin antelope squirrel can be made.
Image Caption: San Joaquin antelope squirrel. Credit: BLM/Wikipedia