Predator harassment is an anti-predator behaviour that may increase a harasser’s risk of predation but decrease the potential for predation for other members of a group. The Cape ground squirrel (Xerus inauris) is a facultative cooperative breeder from southern Africa that harasses venomous snakes. The objective of my study was to examine predator harassment to determine: 1) whether predator harassment was part of alloparental care by comparing harassment behaviour among age and sex classes; 2) how individuals adjusted their behaviour against different snake species; 3) whether olfaction was used in discrimination of snakes; and 4) if individuals possessed venom resistance against venomous snakes. I found that females with juvenile offspring harass snakes longer and more intensely than other individuals, suggesting that predator harassment was a maternal behaviour. Squirrels increased harassment, inspection and vigilant behaviours with risk when exposed to both live snakes and snake odours suggesting they can use olfaction to discriminate snake predators. I also found no venom resistance in Cape ground squirrels concluding the cost of envenomation was significant.

The introduction of nonnative salmonids into Southern Appalachia may pose a threat to resident salamander populations. In recent years, the stocking and encroachment of rainbow trout (Oncorhynchus mykiss) into headwaters where the black-bellied salamander (Desmognathus quadramaculatus) and brook trout (Salvelinus fontinalis) naturally coexist has raised concerns. In aquatic prey, predator-avoidance responses are primarily influenced through the detection of chemical cues released from predators. The objective of this study was to determine how co-occurrence with a predator influences black-bellied salamander predator recognition behavior. To evaluate this, salamander activity metrics (general activity, number of movements, and latency to move) were recorded before and after exposure to either native trout predator cue (brook), introduced trout predator cue (rainbow), or conditioned tap water (control). Larvae were collected from different streams based on their trout predator assemblage with larvae coming from brook, rainbow, rainbow/brook, and no trout stream reaches. Our results show that larvae that co-occur with trout reduced their activity when exposed to brook trout predator cue, but their response to rainbow trout predator cue depended on their previous co-occurrence. Larvae from areas with only brook trout exhibited a weak predator-avoidance when exposed to rainbow trout predator cue. A follow-up test to determine the influence of alarm cue on predator response in these larvae indicated that the alarm cue enhanced the response to the rainbow trout predator.

The ability of prey to detect and respond appropriately to predator risk is important to overall prey fitness. Many aquatic organisms assess risk through the use of chemical cues that can change with predator diet. Two variable characteristics of diet are: 1. prey type and 2. prey mass. To assess the effect of these two characteristics on the assessment of risk by the mud crab Panopeus herbstii, I exposed mud crabs to the urine of the blue crab Callinectes sapidus fed one of 5 diet treatments: 10g of oyster shell free wet mass, 5g of oyster shell free wet mass, 10g crushed mud crabs, 5g crushed mud crabs, and a mix of 5g of oyster shell free wet mass and 5g crushed mud crab. Effects on P. herbstii foraging were tested in a previously developed bioassay by measuring shrimp consumption over a 4 hour period. I hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a diet of crushed mud crabs than to urine from C. sapidus fed a diet of oysters. I further hypothesized that P. herbstii would have a larger magnitude response to urine from C. sapidus fed a high mass diet relative to a lower mass diet. Contrary to expectations there was no observed effect of urine on P. herbstii foraging in any of the treatments. Results suggest that bioassay protocol may be unreliable suggesting further replication to determine the difference between this study and previous results. Future studies examining how P. herbstii varies with urine concentration will aid in understanding the ecological scale of this predator cue system. Determining the role of other potential cue sources will improve the predictive abilities of these studies.

When multiple predators foraging together have different individual consumption rates than predators foraging in isolation, they exhibit non-independent multiple predator effects on prey. I examined multiple predator effects in a system consisting of invasive green crabs (Carcinus maenas L.), native rock crabs (Cancer irroratus Say) and benthic macrofauna prey. First, I examined multiple predator effects when green crabs and rock crabs forage on soft-shell clams (Mya arenaria L.) in different habitat types (sand, sand with artificial seagrass) and assessed the behavioural mechanisms responsible for the observed predation effects. Independent multiple predator effects on prey were detected for most conspecific and heterospecific pairs in both habitat types. In general, crab foraging behaviours were not affected by the presence of another predator. Interactions between predators did not influence foraging behaviours because encounters were infrequent, short in duration and predominantly non-aggressive. A non-independent multiple predator effect on prey (marginally significant) was observed when green crabs foraged with rock crabs in artificial seagrass. This effect, however, could not be explained by the observed crab behaviours. Second, I investigated multiple predator effects when green crabs and rock crabs forage on a soft-sediment macrofauna community. Because crabs did not have significant predation effects on the community throughout the experiment, I did not evaluate multiple predator effects on prey. It is possible that crab predation was not important in regulating the macrofauna community, in which case multiple predator effects were non-existent. Predation may have been suppressed due to a combination of factors, including interactions between predators, harsh environmental conditions or a sub-optimal prey field. Alternatively, my ability to detect significant predation effects may have been hindered because of prey movement in and out of cages or low statistical power. Overall, results from this thesis demonstrate that multiple predator effects on prey may differ with habitat and highlights the importance of conducting behavioural observations to better understand interactions between predators and the resulting consequences for prey. Multiple predator effects on a soft-sediment community should be re-evaluated to assess the importance of these crab species in regulating benthic macrofauna under natural conditions.

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The systems of interest in this study are the spread of epidemics and invasions from a small propagule introduced into an arena that was initially devoid of the given species or stage of illness. In reaction-diffusion models, populations are continuous. Populations at low densities have the same growth functions as populations at high densities. In nature, such low densities would signify extinction of a population or of a disease. This property can be removed from reaction-diffusion models by small changes in the formulation so that small populations become extinct. This can be achieved by the use of a threshold density or an Allee effect, so there is negative growth at low densities. Both these alterations were made to the Fisher model, a predator-prey model and a two stage and a three stage epidemic model. A semi-numerical method, termed the Shooting method, was developed to predict the shapes and velocities of these wave fronts. This was found to correctly predict the velocity, the peak density of the invading stage or species and the width of the wave front. It was found that in oscillatory cases of the multi species models, a high threshold can remove the wave train or wake which would normally follow the wave front, so the wave becomes a soliton. The next step is to investigate probable causes of persistence behind the initial wavefront. To do this, discrete time and space versions of the models were formulated so that experiments investigating persistence can be carried out in a two dimensional arena with less computational effort. The formulations were chosen so that at reasonable time and space steps the discrete models show no behaviour different to that of the reaction diffusion model, and so that the Shooting method could also be used to make predictions about these wavefronts. Three mechanisms of persistence are investigated; environmental heterogeneity, long range dispersal and self organised patterns.

Predators select for defensive adaptations, such as stings, toxins, and camouflage color patterns. Madtoms, Noturus, are diminutive catfishes with dorsal and pectoral stings. Thirteen of the 25 nominal species have serrated spines in the pectoral sting and a contrasting pigment pattern. Behavior of two saddled species, N. miurus and N. hildebrandi, and one uniformly colored species, N. leptacanthus, was investigated to test if the pigment pattern is camouflage. Saddle spacing and crypticity of the saddled species were measured against various substrates and were found to be unevenly spaced, which could be camouflage when viewed against gravel. Given substrate choices, madtoms preferred gravel during daylight conditions. In subsequent experiments, all species were given colored gravel to test color vs. texture-based substrate choice and preferred dark substrates. In the presence of a predator stimulus, madtoms preferred gravel at night and dawn. The pigment pattern likely is camouflage when viewed against gravel substrates.

Evolution can occur rapidly, along timescales that are traditionally regarded as 'ecological'. Despite growing acceptance among biologists of rapid evolution, a strong paradigm of contemporary evolution is still absent in many sub-disciplines. Here I apply a contemporary evolution viewpoint to conservation biology. Specifically, I examine the impact of cane toads (Bufo marinus) on Australian snakes. Toads were introduced into Australia in 1935, have spread rapidly and represent a novel, extremely toxic prey item to na�ve Australian predators (including snakes). Based on dietary preferences and geographic distributions I find that 49 species of Australian snake are potentially at risk from the invasion of the toad. Furthermore, examination of physiological resistance to toad toxin in 10 of these �at risk� species strongly suggests that most species of Australian snake are poorly equipped to deal with a likely dose of toad toxin. Even species that are highly resistant to toad toxin (such as the keelback, Tropidonophis mairii) face indirect fitness costs associated with consuming toads. Within a population of snakes however, the impact of toads is unlikely to be random. For example, the examination of several component allometries describing the interaction between snakes and toads revealed that, within a species, smaller snakes are more likely to ingest a fatal dose of toad toxin than are larger snakes. Further consideration of the interaction between snakes and toads suggests that toads will not only be exerting differential impact on snakes based upon morphology, but also exert non-random selection on prey preference and resistance to toad toxin in snake populations. To examine the possibility of a morphological response by snakes to toads, I examined changes in the body size and relative head size of four species of snake as a consequence of time since exposure to toads. Two of the species (green treesnakes and red-bellied blacksnakes) are predicted to face strong impacts from toads. These two species showed an increase in mean body size and a decrease in relative head size as a consequence of time since exposure to toads; both changes in an adaptive direction. In contrast, the other two species (keelbacks and swampsnakes) are predicted to face much lower impact from toads, and these two species showed little or no evidence of morphological change associated with time since exposure to toads. These results indicate an adaptive change in morphology at a rate that is proportional to the predicted level of impact for each species, strongly suggesting an evolved response. Red-bellied blacksnakes (a toad-vulnerable species) were further assessed for evolved responses in prey preference and toxin resistance. Comparisons between toad-exposed and toad-na�ve populations of blacksnakes revealed that snakes from toad-exposed populations exhibited slightly higher resistance to toad toxin and a much-reduced tendency to eat toads, when compared with toad-na�ve snakes. Na�ve snakes exhibited no tendency to learn avoidance of toxic prey, nor were they able to acquire resistance to toxin as a result of several sub-lethal doses, suggesting that the observed differences between populations is evolved rather than acquired. Together, these results strongly suggest that blacksnakes are exhibiting an evolved shift in prey preference and toxin resistance as a consequence of exposure to toads. Thus, it appears that snakes are exhibiting adaptation at multiple traits in response to exposure to toads. Given the high likelihood that these adaptive shifts have an evolved basis, it appears that the impact of toads will decrease with time in many snake populations. But what about toads? Because the outcome of the interaction between a toad and a snake is also mediated by the body size and relative toxicity of toads, it is important to understand how these traits vary in space and time. Exploratory analysis revealed that toads exhibit a decrease in body size and a decrease in relative toxicity as a consequence of time since colonisation, indicating that their impact on native predators decreases with time. Additionally, there appears to be meaningful spatial variation in toad relative toxicity, indicating that some populations of native predators are facing higher impact from toads than others. Overall, these results clearly indicate the importance of assessing the potential for rapid evolutionary response in impacted systems. Doing so may provide evidence that some species are in less trouble than originally thought. Additionally, and as more data accumulate, it may be possible to characterise certain categories of environmental impact by their potential for eliciting adaptive response from �impacted� species. This approach has strong implications for the way conservation priorities are set and the way in which conservation dependent populations are managed.

The ability to detect and react to a predator odour is crucial for prey species. In the present study 10 mice (Mus musculus) were used to test the behavioural response of mice towards two predator odours (3-methyl-1-butanethiol and 3-mercapto-3-methyl-butan-1-ol) and one fruity odour (n-pentyl acetate). All three odours were tested against a near odourless blank stimulus (diethyl phthalate). The animals were individually placed in a test chamber of two equally sized compartments divided by a vertical Plexiglas wall with a semicircular opening. Their proximity to the odours, placed beneath the floor in petri dishes in each compartment, was measured continuously with stop watches. The mice spent less time in proximity to 3-methyl-1-butanethiol and n-pentyl acetate compared to diethyl phthalate (P<0,05). The mice did not prefer any specific compartment in the test with 3-mercapto-3-methyl-butan-1-ol compared to diethyl phthalate (P>0,05). The avoidance of 3-methyl-1-butanethiol and n-pentyl acetate can be explained either by neophobia, or in the case of 3-methyl-1-butanethiol that it contains sulphur. The lack of behavioural response towards 3-mercapto-3-methyl-butan-1-ol may be due to its loss of intensity over time. From this study it is not certain if mice have an innate fear of predator odours.