Differences in Escape Behavior between Cryptic and Aposematic Frogs

Escape Behavior Differences in Cryptic and Aposematic Frogs

·         During one of our class presentation, we learned all about aposematic coloration in frogs. Along with coloration the various studies looked at relative toxicity, mating, and the relative predator preference by color. One experiment conducted by Hegna, Saporito and Donnelly used adorable clay models to mimic the exact shades of brown, red, and green seen in three frog species as a way to test relative predation based on number of attack. The clay models were placed on the forest floor and after a specified time the experimenters simply counted the number of etch marks in the clay and tallied each one as a predator attack. The experiment found that green was attacked the most, red an intermediate number of times, and brown the least (Hegna, Saporito and Donnelly).  

·         It appears from this study that less predator attempts were made on red frogs, likely due to their warning coloration acting as a predator defense. However, Ozel and Stynoski have qualms regarding this study’s over simplified approach since they failed to account for a crucial component of prey-predator interaction: prey escape behavior.

·         This study investigates what the clay models could not, differences in prey escape behavior when faced with an incoming predator.

·         In most of the animal kingdom the Fight or Flight instinctual response is actually Fight, Flight or Hide. This third component highlights the importance of regulating resources whether that means not wasting energy fleeing or not leaving a suitable/plentiful habitat. Escape behaviors should only be performed when the threat of danger is immediate and the calculation of when the risk is substantial enough to flee is determined by several factors. Optimal escape theory of Ydenberg and Dill looks at the trade-offs between staying in place and deciding to flee using a measurement known as flight initiation distance (FID), or the distance from predator to prey when the prey begins escape behavior (Ydenberg and Dill).

·         Aposematic coloration is a defense strategy designed to warm potential predators of dangerous qualities of the prey, frequently that they are poisonous, by displaying noticeable often bright colors. Cryptic coloration takes an opposite approach in an effort to camouflage the prey and have it go undetected. Based only on the dramatic differences in defense strategy it is likely that escape behavior varies according to coloration.

·         The current study investigates differences in escape behavior between the aposematic poison frog, Oophaga pumilio and the cryptic frog, Craugator bransfordii, both of which can be found in the forests of Costa Rica (Ozel and Stynoski).  

·         The experiment measured the distance between the frog and the human observer at the moment that frog began escape flight. They also recorded the distance traveled by the frog from initial flight spot to final landing position, with turns and multiple hops accounted for.

·         Although it has often been suggested that there are differences in escape behaviors between aposematic and cryptic frogs, this study was the first to show in a field study that there is indeed reduced escape behavior in aposematic frogs when compared to cryptic frogs.

·         This study not only compared cryptic to aposematic but also analyzed the influence of sex and vocalization ability on escape behavior by comparing the flight initiation distance of cryptic frogs, female aposematic, non-vocalizing male aposematic, and vocalizing male aposematic frogs. As we know from discussions in class vocalization in frogs is costly, it takes up a lot of energy and is used not only in courtship but also in territory defense. The results of this study showed that vocalizing aposematic males had the lowest flight initiation distance of any group, and often failed to flee at all. This behavior is likely a decision related to their anti-predator mechanism combined with their territorial tendencies to stay put. Fleeing might lose them their territory and reduce chance of mating which would lower fitness. This explanation of the observed behavior is supported by the high flight initiation distance seen in non-vocalizing aposematic males and aposematic females. Aposematic males that did not flee frequently turned their dorsum up towards the predator since this is the area where toxins are most concentrated they might harm the predator without losing their position within their territory.

·         This research adds to our knowledge of cryptic versus aposematic coloration in frogs and their variation in strategy for survival. The differences observed between sexes where males are more likely to defend a territory and females are more likely to flee since are often sought out and do not have to worry about courtship or losing mating opportunities as much as males do. The differences between vocalizing and non-vocalizing groups further illustrate the energy expense of vocalization (since they don't want to waste energy fleeing) as well at the importance of vocalization in establishing territory. The vocalizing males are willing to go to great  lengths in order to defend their territory, whereas non-vocalizing males show behaviors more similar to the females.  

This is a summary of Differences in Escape Behavior between Cryptic and an Aposematic Litter Frog 

By:   Ozel, L.D. and Stynoski, J.L.

http://eds.a.ebscohost.com/ehost/detail?sid=763b053d-fee6-4285-9f93-37fb66c356e4%40sessionmgr4001&vid=1&hid=4111&bdata=JnNpdGU9ZWhvc3QtbGl2ZSZzY29wZT1zaXRl 

Work Cited

·         Hegna, R.H., Saporito, R.A., and Donnelly, M.A. (2013). Not all colors are equal: predation and color polytypism in the aposematic poison frog Oophaga pulilio. Evol Ecology. 27: 831-845.

·         Ozel, L.D. and Stynoski, J.L. (2011). Differences in Escape Behavior between Cryptic and an Aposematic Litter Frog. Journal of Herpetology. 45(3): 395-398.

·         Ydenberg, R.C. and Dill, L.M. 1986. The economics of fleeing from predators. Advances in the Study of Behavior. 16:229-249.