A major cause of mortality of Richardson's ground squirrels is predation.  Main predators include long-tailed weasels, badgers, hawks and falcons.

Long-tailed weasels (Mustela frenata)

  Long-tailed weasels raid nests in search of infants, and weasel predation alone can reduce the juvenile population by 50% during a single season.  Long-tailed weasels are able to kill adult ground squirrels, especially by cornering them underground.  However, adult ground squirrels avoid capture by remaining above ground and will even attack weasels above ground.

Badgers (Taxidea taxus)

Although North American badgers occasionally ambush ground squirrels above ground, they specialize in digging ground squirrels out of their burrows.  This method of hunting is especially effective in autumn when the ground squirrels are torpid and the ground is not yet frozen.  Badgers can capture up to 50% of hibernating ground squirrels in areas of high prey density.  Because of their ability to use excavation to capture hibernating ground squirrels, badgers are the only predators that hunt ground squirrels both in the summer and winter.

Hawks (buteos) and Falcons

During the chick-rearing period in southern Alberta, Richardson's ground squirrels account for over 75% of total prey biomass for ferruginous hawks (Buteo regalis), red-tailed hawks (Buteo jamaicensis), and Swainson's hawks (Buteo swainsoni).  Although hawk and falcon populations are relatively small when compared to those of ground squirrels, hawks and falcons have been estimated to kill 15% of a ground squirrel population in one season.  A single pair of ferruginous hawks raising a brood of chicks is estimated to consume over 400 ground squirrels in a season.

Male Richardson's ground squirrels seem to be more susceptible to aerial predation than females are, in part because males are the only prey above ground in early spring and in autumn (see Annual Activity Cycle), in part because males are not as wary as females during the mating season, and in part because dispersing males are more at risk than sedentary females.

Other Predators

Other predators include bald eagles (Haliaeetus leucocephalus) and great horned owls (Bubo virginianus), both of which target adults and juveniles.  Terrestrial predators such as the red fox (Vulpes fulva) and coyote (Canis latrans) also feed on both adult and juvenile ground squirrels.  In contrast, prairie rattlesnakes (Crotalus viridis) primarily capture juveniles, and will often seek them out in their burrows.  Domestic cats and dogs also hunt ground squirrels.

Parasites
 

A with most animals, including humans, Richardson's ground squirrels are host to a large array of parasites.

Ectoparasites

Flesh Flies

Neobellieria citellivora, formerly known as Sarcophaga citellivora and more commonly known as a flesh fly, is one of the most devastating parasites of the Richardson's ground squirrels.  Found in southern Alberta, the adult fly lays live larvae primarily on the backs of ground squirrels. The larvae, commonly called maggots, then burrow beneath the skin and begin feeding.

Infested ground squirrels are known to carry burdens of anywhere from 80 to over 200  larvae at one time, probably a result of multiple strikes on a single host.  Death of the ground squirrel by myiasis is inevitable and is estimated to occur within seven days of initial larviposition. Juveniles, especially juvenile males, are the most common targets.  data

Although reported from only two populations of Richardson's ground squirrels, both in southern Alberta, fly myiasis can account for the deaths of 10-15% of juvenile males.

Other ectoparasites include mites, lice, fleas and ticks.

When squirrels emerge from hibernation they are sometimes heavily infested with fleas, commonly 20 to 30 per individual, but by summer these numbers are reduced to one or two fleas per individual.  Although two species of fleas found on ground squirrels, Opsicrostis labis and Oroplylla rupestris, are known vectors of the plague, there have been no confirmed reports of plague in Alberta for over 60 years.  The effects of flea-transmitted diseases on ground squirrel populations are not yet known.  Other potential vectors of disease are ticks such as Dermacentor andersoni, a carrier of Rocky Mountain spotted fever and tularemia, but again no human cases have been reported recently.  Ectoparasites such as fleas tend to have strong host preferences and rarely jump from ground squirrels onto humans or human pets.
 

Endoparasites

Endoparasites include the microscopic single-celled coccidians found in the digestive tract, as well as trypanosomes found in the bloodstream, lymph and spinal fluid.

Larger parasites include flatworms (cestodes and trematodes).  Richardson's ground squirrels may also be infested by nematodes such as hookworms, pinworms and roundworms, as well as acanthocephalans or spiny-headed worms.

Even given this variety, the most common parasitic worm, the helminth Citellinema bifurcatus, has been found in less than one third of ground squirrels in Saskatchewan.  Males and older squirrels are more commonly infested than females or juveniles.
 
 

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