Assessment and defence of solitary kangaroo rats under risk of predation by snakes

Abstract

Prey that spend a large proportion of their time foraging must trade-off between predator defence and feeding. Because predation risk can be a cost in desert granivores, we predicted that kangaroo rats (Dipodomys) should weigh the risk of predation when deciding which behavioural option to pursue. We manipulated apparent predation risk of the giant kangaroo rat, D.ingens, and the desert kangaroo rat, D.deserti, and predicted they should be more vigilant and show greater defensive behaviour to the more dangerous stimulus of a real snake than to an artificial snake decoy. Results showed that kangaroo rats decreased foraging with increased vigilance when the snake and decoy were present. The largest decrease in foraging was in response to the live snake, and both species oriented towards, approached and footdrummed more in the presence of the live snake than the decoy. The species also differed in their antipredator behaviour: D.ingens footdrummed more and spent more time within striking distance of the snake than the decoy. Dipodomys deserti spent more time within 1m of the snake than the decoy and kicked sand at the snake. Sand kicking was never observed inD.ingens . We conclude that kangaroo rats are able to discriminate predation risk. They decrease foraging and increase vigilance in the presence of live snakes to assess risk and may approach and footdrum as a pursuit deterrent to communicate to the snake its chances of ambush are no longer available to cause the snake to leave. Sand kicking may function to harass the snake to cause it to leave.