It’s no secret that every animal has a predator that they work hard to avoid. To do this, animals display actions called anti-predator behaviors, which are behaviors they use to respond to the presence of danger or even to avoid it completely. We have all seen this happen on TV, in zoos, and even in our backyards. Zebras run from lions, meerkats feign death from hawks, leaf bugs blend into their environment. . . It’s all over the animal kingdom! As it turns out, some animals have more than one way to protect themselves from predators and sometimes one strategy may be stronger than another. Researchers Cameron Hudson, Gregory Brown, and Richard Shine were curious to know if cane toads (Rhinella marina) display a preference of anti-predator behaviors depending on their geographic location. Cane toads are found to respond to predators by spraying a toxin out of a gland on their shoulders or by fleeing, but there seemed to be no understanding of which behavior they chose to do first when faced with danger. To answer this question, cane toads were collected from around the world and the researchers conducted a study on their anti-predator behaviors.
Despite being native to South and Central American, Cane toads have moved all around the world and become invasive. By moving to different geographical conditions, they experience different predators and harmful situations where they may be more inclined to either flee or use their special toxin to protect themselves. To test different geographic locations, cane toads were collected from Queensland, Australia; Western Australia; Hawaii, United States; New Guinea; and Northern Territory, Australia. In total, there were 642 cane toads collected from all the locations over the course of the 2-month study. The toads were measured and then randomly selected to participate in a hopping experiment. The trial was to determine the amount of times they could hop through it, how many times they hopped, and if they released any toxin during the hopping trial. The trial was designed to have them respond as if there was a predator. To get them in the anti-predator behavioral mode, researchers would poke them with a blunt pole. If the individuals did not respond after being poked ten times, they were excluded from the study.
The study found that the cane toads with longer legs would more likely to flee than the cane toads with shorter legs, despite where they came from. There seemed to be no significant geographic influence on their likelihood to release the toxin when faced with a predator. Toads that refused to move during the hopping trial were found to be more likely to release the toxin first, unlike the toads who did hop in the trial and released the toxin later when they started feeling exhausted. There was an effect of geographic location on the toad’s overall anti-predator tactics, which included all the strategies they could have used. The study found that cane toads from Australia were more likely to flee and toads from Hawaii and New Guinea preferred to release the toxin. These results may be influenced by the type of predators they are faced with, as well as the landscape they may be colonized in.
The results of this study observe an important aspect of the evolution of behavior, specifically with predation. The researchers provide just one example of how species can change based on geographic location and influence of other species. In this case, cane toads from areas of less predation seemed to respond slower than toads from areas of higher predation. Overall, the cane toads are shown to have aspects of developmental plasticity and heritability in their anti-predator behaviors which allows them to adapt to their environment quickly and to understand how to best utilize their tools. This leads us to wonder how many other species display similar situations and how were can better understand their adaptive behavior.
Article citation: Hudson, C. M., Brown, G. P., & Shine, R. (2017). Evolutionary shifts in anti-predator responses of invasive cane toads (Rhinella marina). Behavioral Ecology and Sociobiology,71(9). doi:10.1007/s00265-017-2367-4
