What Happened to the Franklin's Ground Squirrel?

"I remember seeing them a lot when I was a kid. Where did they go?" "Those things used to be all over the place 30 years ago, but I haven't seen any around in quite some time." "During my 20 years as a wildlife biologist, I have only seen this species once." These comments are typical in reference to the Franklin's ground squirrel. It seems to be one of the many species in the Midwest that has become uncommon over the last several decades.

The Franklin's ground squirrel is a rather secretive critter. It can most often be found in tall, dense grassland vegetation and rarely spends time in open areas. It is slightly larger than its more common cousin, the thirteen-lined ground squirrel, and its coat is gray with no striping. At first glance it might be mistaken for a gray tree squirrel but the Franklin's has a smaller, narrower head and its tail is shorter and less bushy. It feeds primarily on plant matter but will also consume insects, carrion, and bird eggs.

The Franklin's ground squirrel can be found throughout much of the Midwest, from central Kansas to Indiana and northward through the Dakotas to Manitoba, Canada; however the species appears to be on the decline in a large portion of its range. Indiana, Wisconsin, and Iowa have awarded the Franklin's ground squirrel conservation status and wildlife biologists in Missouri have expressed concern over the species. In Illinois, these ground squirrels historically ranged throughout most of the northern two-thirds of the state but a lack of recent sightings has led to concern over their fate here as well.

In 2001 Joyce Hofmann (Center for Biodiversity), Ed Heske (Center for Wildlife Ecology), and I conducted a mail survey of 166 wildlife professionals throughout Illinois in order to gather information pertaining to the current status of the Franklin's ground squirrel. Only 9 of the 77 respondents knew of currently existing populations, describing a total of only 11 individual colonies. Forty-four areas of possible occurrence were also described based on unconfirmed sightings, the existence of historical records, or the existence of appropriate habitat. Based on this information, I conducted live-trapping surveys at 24 sites of suggested current occupancy and found Franklin's ground squirrels at only 2 of them.

Loss of appropriate habitat has been cited by many as the cause of the decline of the Franklin's ground squirrel. The loss of grassland and prairie habitat to agriculture has been well documented; however the reason for this species' decline may not be as simple as sheer habitat loss. Many of the areas I surveyed that did not contain the species still appeared to have appropriate ground squirrel habitat. So, if appropriate habitat still remains to some degree, then why is the Franklin's ground squirrel not as common as it used to be? The answer probably has to do with the current overall structure of the remaining grasslands.

The remnants of the once-vast contiguous prairie system exist today in a highly fragmented state. As these habitat patches decrease in size they become less capable of supporting self-sustaining wildlife communities due to decline in resource availability and increasing competition for what little remains. Only generalist or highly mobile species that are capable of utilizing resources from multiple patches and habitat types are able to adapt to this new landscape. Further complicating the situation is the lack of connectivity between the remaining grassland patches, which for the most part exist as isolated islands in a sea of agriculture. Habitat corridors between two or more patches may provide a lifeline through which animals from each patch may travel, thereby increasing resource availability and providing a means of maintaining genetic fitness through the exchange of individuals.

Franklin's ground squirrel, given its preference for thick vegetation, may be unlikely to cross the expanses of agricultural fields, urban areas, and mowed roadways that separate grassland patches. This would leave each colony isolated, and thus more vulnerable to extirpation. Currently this scenario, although probable, is only hypothetical. My research is beginning to explore the effects of fragmented habitat structure on Franklin's ground squirrel. During the summer of 2002, I will be radio-tracking juvenile squirrels throughout their dispersal in order to examine movement patterns and specific habitat usage.

Habitat fragmentation and isolation may be only one contributing factor to the species' decline. Issues such as interspecific competition, increased predation rates, and changes in overall habitat quality are probably involved as well. However, management on a regional scale focusing on landscape issues such as the consequences of habitat fragmentation ultimately may better serve to protect the Franklin's ground squirrel rather than small-scale management of individual populations.

Jason Martin, Center for Wildlife Ecology

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