Tucson Standard

The Mount Graham red squirrel, a species once believed extinct in the 1960s, has adapted to survive in the Pinaleño Mountains of southeastern Arizona. This squirrel is isolated from other red squirrels and faces environmental challenges such as wildfires and droughts. To endure periods of food scarcity, these squirrels use two primary hoarding strategies: larders, or middens, and scattered caches.

A study by Sean Mahoney and Bret Pasch from the University of Arizona's Mt. Graham Biology Programs analyzed these hoarding behaviors. Published in the journal Animal Ecology, their research examined a 25-year dataset on Mount Graham red squirrels and included behavioral data for nearly 40% of all mammal species that cache food.

"We incorporated data on nearly all mammals that cache food, whether they feed on seeds, mushrooms or other animals," said Mahoney. "Tree squirrels are particularly interesting because scattered cones once forgotten can influence forest regeneration."

The study found that temperature and population density significantly impact hoarding behavior. In general, colder temperatures and higher population densities were linked to larder hoarding. However, variations in mean annual temperature over 24 years did not correlate with changes in the Mount Graham red squirrel's behavior. Instead, lower population numbers led to reduced investment in larder hoards due to competition for food and theft among animals.

"Squirrels appear to be sensitive to their social environment," explained Pasch. "Increased rates of petty theft can occur at higher densities."

The findings provide valuable insights for conservation efforts. Biologists have traditionally used middens as an index of squirrel population size but may need alternative methods if scatter hoarding becomes more common due to changing environmental conditions.

"The data suggests that we need to be mindful of population density and temperature," Mahoney noted. This research highlights how understanding animal behavior can aid adaptive conservation management strategies as habitats change.