Abstracts (first author)
Do prey respond appropriately to evolutionarily novel predators?PDF
Deserts provide a model system for studying convergent evolution. Sand dunes in the Mojave (USA) and Negev (Israel) deserts are home to distinct yet convergent community of species with granivorous rodents and sidewinding vipers, red foxes and barn owls as predators. By virtue of heat sensing pits(vipers) and external cheek pouches (hetromyid rodents) the Mojave possess constraint breaking adaptations over the counterpart species in the Negev.
In a semi-natural arena, we exposed Merriam’s kangaroo rat (Dipodomys merriami) and desert pocket mice (Chaetodipus penicillatus) of the Mojave, and Allenby’s gerbil (Gerbillus andersoni allenbyi) of the Negev to sidewinder rattlesnakes (Crotalus cereastes), a pit viper, and to the Saharan horned viper (Cerastes cerastes). We quantified the response of each rodent species to the snakes and in combination with owls. We monitored activity over all moon phases and asked whether the rodents responded differently to the novel, compared to the familiar, snake species. Specifically, we test the recognition of gerbils of a novel predator with heat sensing pits, and heteromyids’ assessment of a snake with limited tools.
Analysis shows that the gerbiline rodents, at first, risk encounters with the novel viper before rapidly learning to avoid both vipers. Lengthy exposure allowed gerbils to adjust and optimize their balancing of food and safety. This caused a 25% increase in foraging for both species of vipers. Pocket mice reduced their foraging equally regardless of viper species. Interestingly Kangaroo rats found both species equally frightening following exposure they ceased to be aversive of the novel predator.
Evolutionarily convergent rodents do not converge on predator evasion strategyPDF
Merriam’s kangaroo rat (Dipodomys merriami) and desert pocket mice (Chaetodipus penicillatus) of the Mojave Desert and Allenby’s gerbil (Gerbillus andersoni allenbyi) of the Negev Desert are granivorous rodents inhabiting desert sand dunes. These dunes are home to the sidewinder rattlesnake (North America) and the horned viper (a sidewinding snake of the Middle East). The gerbils in the Negev evolved with the Saharan horned viper (Cerastes cerastes) and the Mojave Desert rodents evolved with the sidewinder rattlesnake (Crotalus cerasts). Both predators and prey species in the Mojave are convergent to the Negev counterparts: The snakes have heat sensing pits and the rodents have fur lined cheek pouches.
We exposed the three rodent species to both snake species in a test system and measured the inherent knowledge they possess on the predators. The process was repeated after two months of exposure to both snakes to understand what knowledge was acquired when the predation risk was real and the selective pressures it puts on the population. We were interested in seeing how the species view the evolutionarily know and novel predators, and to assess whether the rodents learnt the strengths and weaknesses of the snakes in relation to each other.
We found that each species employs a different strategy in response to the predators. Gerbils learnt that the pit vipers are dangerous by decreasing the amount of time they spend foraging in their presence by 80% and forage 25% less food in those patches. Desert pocket mice avoid snakes overall and decreased the time they spend in the presence of the known predator (the pit viper) by 90%. Lastly Kangaroo rats employed an “in your face” predator management strategy. They doubled their foraging time in the presence of the novel predator with an increase of 13% in foraged grain. This suggests that these species who are functionally convergent may not be behaviorally convergent.