Antipredator responses

Responses of amphibians to chemical cues of predators could include behavioral and morphological defenses, as well as alterations in life-history characteristics. The majority of research to date has focused on behavioral responses, however, the importance of chemical cues in the other types of defenses warrants attention. 

In one study, Kats (1988) plugged the external nares of small-mouthed salaman- 

Few studies have examined the responses of terrestrial amphibians to chemical cues from predators. In one study, two plethodontids (Plethodon dorsalis and P. richmondi) were tested for an avoidance response to chemical cues from ringneck 

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Tadpoles of the two closely related frog species Rana lessonae and Rana esculenta respond more to chemical cues of their predator, the pike E. lucius, than to visual and tactile ones. The strongest swimming, resting, and edge-use behaviors - all considered antipredator responses - occurred to a combination of... 

Brown, G. E., Adrian, J. C., Jr., Naderi, N. T., Harvey, M. C., and Kelly, J. M. (2003). Nitrogen oxides elicit antipredator responses in juvenile channel catfish, but not in convict cichlids or rainbow trout conservation of the ostariophysan alarm pheromone. Journal of Chemical Ecology 29,1781-1796. 

Brown, G. E. and Smith, R. J. F., Conspecific skin extracts elicit antipredator responses in juvenile rainbow trout (Onchorrhynchys mikiss), Can. J. Zool., 75, 1916, 1997. 

Antipredator Responses by Intertidal Gastropods to Chemicals from Starfish... 

Baumgartner D, Koch U, Rothhaupt KO (2003) Alteration of kairomone-induced antipredator response of the freshwater amphipod Gammarus roeseli by sediment type. J Chem Ecol 29 1391-1401... 

Ferrari MCO, Messier F, Olivers DP (2008) Variable predation risk and the dynamic nature of mosquito antipredator responses to chemical alarm cues. Chemoecology 17 223-229... 

Carreau-Green ND, Mirza RS, Martinez NL, Pyle GG (2008) The ontogeny of chemically mediated antipredator responses of fathead minnows Pimephales promelas. J Fish Biol 73 2390-2401... 

Sakamoto R, Ito A, Wada S (2006) Combined effect of risk type and activity rhythm on antipredator response of the shore crab Gaetice depressus (Crustacea Grapsidae). J Mar Biol Assoc UK 86 1401-1405... 

My goal in this paper is to briefly describe the role of chemical alarm cues in local risk assessment, focusing on threat-sensitive trade-offs. Specifically, I will address the following questions (1) do prey fish show graded responses in overt antipredator responses with decreasing stimulus concentration, (2) are prey fish able to detect chemical alarm cues below their minimum overt behavioural response threshold, and (3) do prey fish exhibit threat-sensitive changes in behaviour in response to alarm cues at concentrations below the minimum overt response threshold ... 

Recent evidence has shown that individuals are able to detect chemical alarm cues well below the overt behavioural response threshold. Fathead minnows were able to acquire the recognition of the chemical cues of a novel predator (yellow perch, Perea flavenscens) if the predator odour was paired with H3NO at concentrations as low as 0.1 nM (25% of the previously demonstrated minimum overt response threshold) (Brown et al., 2001c). Mirza and Chivers (2003) likewise found that juvenile rainbow trout did not exhibit any overt antipredator response (i.e. not different from a distilled water control)... 

Figure 1. A simplified graphical representation of the behavioural response intensity of individual prey as a function of relative chemical alarm cue concentration. Bold line denotes overt antipredator response curve, dashed line denotes covert response curve. Shaded area between overt response threshold (BRTotot) and covert response threshold (BRTcowt) represents concentration range in which we would expect to see threat-sensitive behavioural responses.

Finally, the difference between the overt and covert response thresholds (Figure 1) suggests that there exists a range of concentrations over which individual prey can detect an alarm cue, but do not exhibit an overt antipredator response. Recent studies have begun to examine the role of chemical alarm cues over this low coneentration range. 

There remains the possibility that sub-threshold concentrations of chemical alarm cues may provide information leading to immediate changes in behaviour, even in the absence of an overt antipredator response. These threat-sensitive changes in behaviour may include 1) increased vigilance towards secondary predator cues such as visual information, 2) an increase in risk-aversive foraging tactics and 3) context dependent behavioural shifts in response to conspecific chemical alarm cues. 

Pollock et al (2003) were the first to document the ability of minnows to learn to recognize heterospecific cues as an indication of predation. In their study a naturally occurring population of fathead minnows allopatric with brook stickleback did not respond to the skin extract of stickleback with an antipredator response. Stickleback fish were then introduced into the pond with the minnows and the two species were left to coexist for a period of five years. Following the period of co-existence, minnows were tested in the laboratory for a response to stickleback alarm cues. Not only did minnows now respond to stickleback cues, but they did so with the same intensity as they did to their own conspecific cues. A field experiment was also able to document a significant avoidance of stickleback skin extract in the wild. 

Mirza and Chivers (in press) found that fathead minnows had the ability to learn to recognize a novel heterospecific odour as an indication of predation if the cue was present in the diet of a known predator. In their study, minnows were exposed to chemical stimuli collected from a tank containing a known predator (northern pike, Esox lucius) fed one of two unknown prey, stickleback or swordtails (Xiphophorous helleri). In subsequent behavioural tests, the minnows were exposed to either swordtail skin extract or stickleback skin extract. Minnows exposed to the odour of pike fed stickleback responded to stickleback skin extract with an anti-predator response but did not respond to swordtail skin extract. Similarly, minnows exposed to pike fed swordtail cues responded to swordtail skin extract with an antipredator response but did not respond to stickleback skin extract. This study demonstrated that minnows had the ability to learn to recognize a novel cue in the diet of a known predator, whether that cue is from a species that commonly co-occurs with minnows (the stickleback) or an allopatric tropical species with which it has never co-occurred. 

In nature prey animals might face sustained periods of risk when predators are abundant and in close proximity in contrast, they might experience low risk when predators are sparse and wide ranging (Sih and McCarthy, 2002). Also, depending on the characteristics of the water body, it is possible that alarm cues could be diluted to lower concentrations as well as mixed with other odours from the environment, which may decrease the intensity of prey s antipredator response. Therefore, additional smdies aimed at understanding the importance of graded responses to different concentrations of chemical cue in nature are needed. 

NOCTURNAL SHIFT IN THE ANTIPREDATOR RESPONSE TO PREDATOR-DIET CUES IN LABORATORY AND FIELD TRIALS... 

We conducted a field experiment to examine whether a temporal shift in antipredator responses to predators based on the predator s diet would be observed in a more natural context. We performed the early experiment (conducted between 2030 and 2330 hours) and late experiment (conducted between 2330 and 0230 hours) on a single night in July 2003 following a day of rain so that leaf litter was wet and air was saturated with moisture. Plethodontid activity is generally restricted to moist conditions within a few... 

Ducey, P. K., Anthony, C. D., and Brodie, E. D., Jr., 1991, Thresholds and escalation of antipredator responses in the Chinese saiamander Cynops cyanurus inter- and intra- individual variation, Behav. Process. 23 181-191. 

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