The purpose of the present study was to determine olfactory detection thresholds in human subjects for a set of six sulfur-containing odorants which are known to be components of mammalian predator odors. Using a threealternative ascending staircase procedure, the olfactory sensitivity of 12 healthy adult human subjects, 6 males and 6 females was assessed with 2-propylthietane, 2,2-dimethylthietane, 3-mercapto-3-methylbutan-1-ol, 3-mercapto-3- methylbutyl formate, 3-methyl-1-butanethiol, and methyl-2-phenylethyl sulfide. The results showed that A) all six predator odorants were detected at concentrations below 1 ppb (parts per billion), and one of them (3-mercapto-3-methylbutyl formate) even at a concentration below 1 ppt (parts per trillion), B) structurally similar odorants yielded significantly different threshold values, and C) no significant sex differences were found in olfactory sensitivity with any of the six odorants. The findings obtained from the present study show that human subjects were not generally less sensitive to the predator odorants tested here compared to spider monkeys despite having a markedly lower number of olfactory receptor types. Further, they suggest that humans may be more sensitive to predator odorants compared to a variety of non-predator odorants. One possible explanation for the high olfactory sensitivity observed here is the fact that sulfur compounds typically can be detected at low concentrations. An alternative explanation derives from an evolutionary perspective as our human ancestors were a potential prey of large carnivores and  thus a high olfactory sensitivity for predator odors should be adaptive for humans.

<p>Increased pressure has been placed on researchers to focus on processes at an ecosystem level. However, ecological processes operate at multiple scales from an individual predator up to ocean basin migrations, and research across these scales is extremely difficult. More accurate and detailed understanding of prey distributions relative to physical and biological features can greatly aid in understanding top predator distributions and ultimately ecosystem functioning. High resolution acoustic data is a critical tool that can be used to investigate food web linkages at many spatial scales. At a broad scale, migratory top predators are often modeled relative to oceanographic structure as a proxy for the distribution of their prey. At a fine scale, combining novel technologies including fisheries acoustics, real time oceanographic sensors, and digital tags allows examination of decisions made by an individual foraging whale. In the Gulf of Mexico, fish distributions at fine scales (both horizontal and vertical) were examined relative to hypoxic bottom waters to understand potential ecosystem effects. Forage fish distribution (sand lance, Ammodytes spp.) were measured relative to physical features and oceanographic processes up to the decision making of a top predator, the humpback whale (Megaptera novaeangliae). The effect of geostrophic currents and environmental regimes on the deep scattering layers of the central tropical pacific were examined relative to sightings of marine mammals in the area. Analyses across trophic levels and at multiple scales is an important step towards understanding community ecology and ecosystem processes in pelagic systems.</p> / Dissertation

The endangered willow flycatcher (Empidonax traillii) breeds in mountain meadows in the Sierra Nevada, which have been intensively modified, especially reducing meadow wetness, which favors easy access for mammalian predators to reach nesting areas in the meadow interior. High nest predation frequency is one of the main factors for willow flycatcher and other passerines? populations decline. I conducted trapping in wet and dry areas on 10 meadows in May?August of 2007 and 2008 to identify the assemblage of potential mammalian nest predators. I compared the predator activity between wet and dry areas of the meadows and determined the relationship between predator activity with vegetation and hydrology of the meadows. In 2008, I used radio-telemetry on deer mice (Peromyscus maniculatus) and yellow-pine chipmunks (Tamias amoenus) to determine their movement patterns across wet and dry areas, and between forest and meadow. My results showed that chipmunks? and squirrels? activity was restricted almost to dry areas. The activity of yellow-pine chipmunks was 96% and 97% higher in dry versus wet areas in 2007 and 2008, respectively. Voles, mice, and shrews were active in both site types. Voles (Microtus spp.) and shrews (Sorex spp.) were in general more active in wet areas versus dry areas in 2007. Deer mice were equally active in both site types in 2007 and more active in wet areas in 2008. Between years, predators were 68% more active in wet areas in 2007 compared to 2008, and similarly 52% more active in dry areas. Radio-tagged deer mice used the forest and the meadow and were more common in dry areas, whereas yellowpine chipmunks used more the forest than the meadows and were active only in dry areas. Passerines nesting in drier areas are exposed to a larger assemblage of potential predators and are more likely to be predated. My results suggest that increasing the proportion of inundated areas in the meadows would help reduce predator activity (especially chipmunks and squirrels) and consequently nest predation, helping increase flycatcher numbers. In addition, wetter conditions will favor an increment in food availability for flycatchers and an increment in willow cover, which consequently will provide more nesting substrate and will help increase nest concealment.

The behavioral and physiological interaction between Bufo bankorensis and its snake predators, Macropisthodon rudis and Dinodon rufozonatum were investigated in this study. Adult M. rudis preferred medium sized toads but neonate favored to small ones. About seized position of different toad sizes, adult snakes attacked large toads head first but neonates did randomly. On the swallow direction with toad sizes, adult snakes had no preference but neonates swallowed large toads head first, so the neonates could change the direction swallowing preys after preys had been seized. Adult and neonate snakes spent similar time in handling toads with head first ingestion costed less handling time. After the large rear-teeth had been grounded, M. rudis would spend more time in handling preys. In all trials, venom secreted from parotid glands did not seem to prolong handling time on adult snake. After forced fed 1 mg/g toad venom to D. rufozonatum, no significant change of Na+, K+, Ca2+ ion concentrations were observed but significant increasing of heart rates. The ECGs of intoxicated snakes showed typical digitalis-like cardioactive effects as sinus arrhythmia, prolonged P-R interval as varying degrees of atrioventricular block and ventricular fibrillation. The LD50 of the venom of B. bankorensis are different between from toads sampled Northern and Southern Taiwan. In comparison with dissected toad-eating snakes D. rufozonatum, M. rudis and Rhabdophis tigrinus formosanus, I didn¡¦t find any nuchal glands on nuchal-dorsal site of D. rufozonatum and M. rudis.

Even zooplankton can not be utilized directly by human being; it is an important food source for numerous economical fishes. Zooplankton¡¦s predator-prey interactions can affect not only global carbon fixation, but also fisheries yields directly. Copepods and ciliates are the targets of the current study, which act as critical links between classical diatom-copepod-fish webs and microbial food webs. Analyzing their predator-prey interactions can help us understand more about marine food production. The objective of this study is to investigate the differences in swimming behavior of copepods and ciliates under two environments, which are disturbances and no disturbances of predator-prey. We use five locomotive indicators (NGDR, turning rate, diffusion coefficient, kinetic energy and fractal dimension) to quantify swimming patterns. The trajectories of copepods in the undisturbed situation show circuitous, larger turning angle, and more diffusive behavior, which associate with a lower kinetic energy. The patterns of copepod movement with the presence of prey (ciliates) are contrary to the previous situation. The patterns of ciliates in the undisturbed situation are similar to those of copepods in undisturbed situation, except smaller turning angles. The trajectories of ciliates in terms of the turning and diffusive movement when predators (copepods) show up are different from those of copepods when preys (ciliates) are present. In addition to indicators, this study develops a new encoding scheme for accommodating the spatial-temporal information embedded in the original data. By analyzing the encoded data through some data mining techniques, the predator-prey interactive behaviors in the spatial scale can be easily perceived.

Having means to detect and avoid potential predators is a necessity for prey species. Most mammalian prey species are able to detect odours emitted by predators and to adapt their behaviour accordingly. These odour cues are therefore considered to act as semiochemicals. Predator odours consist of several dozen different odourants. In order to assess if single odourants elicit aversive behavioural reactions, predator-naïve CD-1 mice were presented with six odourants which are part of body-borne odours of different mammalian predator species. A two-compartment chamber was used in order to assess place-preference, motor activity and faecal excretions when the animals were simultaneously presented with a predator odourant and a blank control. Further trials were performed to assess whether the odourant concentrations had an influence on the behaviours. The only odourant that elicited a significant aversion was 3-methyl-1-butanethiol, a compound found in the anal gland secretion of skunks, when presented at a factor of 100 above the olfactory detection threshold of mice. Two other concentrations of 3-methyl-1-butanethiol did not elicit significant behavioural changes. Based on the present study, only one out of six selected predator odourants elicited a significant aversive response in CD-1 mice. This suggests that more than one odour component, or perhaps even the full mixture of odourants, may be necessary for CD-1 mice to respond to a predator odour with aversive behaviour.

The Swedish otter (Lutra lutra) population decreased markedly after the 1950’s and was considered to be seriously threatened for decades. Pollution from industries and other anthropogenic activities were suspected to be the major cause of the decline. The otter is a top-predator in aquatic systems and therefore particularly susceptible to bioaccumulative and toxic substances. For this reason, the species can be regarded as a valuable indicator of environmental health. Today, the Swedish otter population is increasing and has been reestablished in many areas. However, the otter is still missing in some regions of Sweden, especially in the southeast. The aim of this study was to investigate past and present levels, and temporal trends, of environmental contaminants in otters from Småland.The study is based on data of environmental contaminants in liver and muscle tissue from dead otters found in Småland during 1966-2014. I found that the perfluorinated compounds PFOS and PFOA have increased in otters since the 1970’s which is alarming and should be given special concern in future monitoring. Also, while mercury (Hg) is rather stable, selenium (Se) concentrations are decreasing, resulting in Hg exceeding Se on molar mass basis in several otters. This indicates that all of the available Se is bound to mercury, which may imply that the otters are vulnerable to additional Hg contamination. My conclusions are that the present concentrations of the studied environmental contaminants have probably not affected the otter population in general. However, otters may be exposed to toxic levels of some contaminants in certain areas that are more polluted from anthropogenic activities. This could be harmful to individual otters or their reproduction, and therefore, continued monitoring is highly relevant.

Aphids (Hemiptera: Aphididae) are pests of multiple cropping systems, primarily due to the viruses they vector and direct crop damage that is exacerbated by their rapid population growth. In Kentucky, grain aphids (Rhopalosiphum padi and Sitobion avenae) cause significant yield loss to winter wheat as vectors of Barley Yellow Dwarf virus (BYDV), prompting the routine application of insecticides. Coupled with increasing human populations and decreasing arable land, it is increasingly evident that biological control services provided by natural enemies represent a viable long-term management option. Aphids are preyed upon by a diverse array of predators that can be exploited in conservation biological control. I designed a field experiment to monitor dispersal into and out of wheat fields, and how these movements were affected by the surrounding habitat. Analysis revealed there are significant movements of R. padi into the wheat in the fall, and S. avenae in spring, and that these movements are slowed down by forested edges. Natural, field-bordering weed strips were used as a conservation biological technique to enhance predator populations. Results showed that while weed strips did not affect the yield of the crop, aphid abundance, or BYDV incidence, it did significantly increase the abundance of natural enemies. Dominant predators included Coccinellidae, Anthocoridae, Chrysopidae larvae, and Braconidae. Using molecular gut-content analysis, I screened multiple species of predators and found strong trophic linkages between aphids and Orius insidiosus and multiple species of coccinellids, namely Coccinella septempunctata and Coleomegilla maculata. In aphidophagous systems, intraguild predation (IGP) can interfere with the biological control potential so I also screened coccinellids for IGP using newly designed primers. To identify intraguild prey DNA in coccinellids, I designed species-specific primers for C. maculata and C. septempunctata to use in PCR-based molecular gut-content analysis. Results revealed high frequencies of IGP between coccinellids that are significantly higher in weed strip plots. However, I observed no detectable impact on aphid predation during these increased times of IGP, suggesting it does not interfere with biological control of aphids in this system. I discuss the role of weed strips in winter wheat as part of an integrative pest management strategy.

Because differences often exist between species in their tolerances to environmental conditions, locations characterized by extreme parameter values (i.e., high temperature, low DO, high turbidity) may provide refuges from predation or competition by altering the outcome of inter-species interactions. This thesis examined the effects and relative importance of water temperature, dissolved oxygen (DO) and turbidity on habitat use by fish species and resulting changes in community composition. The effects of abiotic factors on predator-prey interactions were tested using field surveys, laboratory experiments, field experiments and computer modeling. Field surveys were conducted in Blind Channel, Delta Marsh, Manitoba, and on Lake Winnipeg, Manitoba, to determine if small bodied forage species preferentially used high temperature, low DO or high turbidity habitats and whether predator species avoided these locations. Prey species were more abundant in these extreme locations at both small (Blind Channel) and large (Lake Winnipeg) spatial scales, but predator avoidance was only documented in Blind Channel. The tolerances of fish species to moderate hypoxia (< 3 mg/L DO) was tested in the laboratory to verify that differences did exist among species and that the observed species distributions were not solely the effect of temperature. To quantify the potential for moderately hypoxic locations to provide a refuge from predation for small fish, a field manipulation was conducted in Blind Channel; hypoxic habitats were created without altering water temperature, decoupling the natural covariation between these two factors that occurs in aquatic systems. The abundance of small forage fish was higher in the hypoxic locations compared to controls and while predators still visited the hypoxic habitats, their mean visit duration was reduced from around 300 min to less than 1 min. An individual based computer model was used to test and illustrate current understanding of the relative importance of temperature, DO and turbidity on predator habitat selection decisions and fish community composition. The model showed that DO had a stronger effect on community composition than temperature, and that reduced foraging success from high turbidity was able to overpower the other two factors. Hypoxia affects habitat selection decisions by fish species and can provide refuges from predation and competition, helping maintain higher species diversity. Water temperature appears to have a weaker effect on fish distributions than DO while turbidity primarily affects visual predators, though the strength of turbidity effects depends on the magnitude and duration of individual events.

Because differences often exist between species in their tolerances to environmental conditions, locations characterized by extreme parameter values (i.e., high temperature, low DO, high turbidity) may provide refuges from predation or competition by altering the outcome of inter-species interactions. This thesis examined the effects and relative importance of water temperature, dissolved oxygen (DO) and turbidity on habitat use by fish species and resulting changes in community composition. The effects of abiotic factors on predator-prey interactions were tested using field surveys, laboratory experiments, field experiments and computer modeling. Field surveys were conducted in Blind Channel, Delta Marsh, Manitoba, and on Lake Winnipeg, Manitoba, to determine if small bodied forage species preferentially used high temperature, low DO or high turbidity habitats and whether predator species avoided these locations. Prey species were more abundant in these extreme locations at both small (Blind Channel) and large (Lake Winnipeg) spatial scales, but predator avoidance was only documented in Blind Channel. The tolerances of fish species to moderate hypoxia (< 3 mg/L DO) was tested in the laboratory to verify that differences did exist among species and that the observed species distributions were not solely the effect of temperature. To quantify the potential for moderately hypoxic locations to provide a refuge from predation for small fish, a field manipulation was conducted in Blind Channel; hypoxic habitats were created without altering water temperature, decoupling the natural covariation between these two factors that occurs in aquatic systems. The abundance of small forage fish was higher in the hypoxic locations compared to controls and while predators still visited the hypoxic habitats, their mean visit duration was reduced from around 300 min to less than 1 min. An individual based computer model was used to test and illustrate current understanding of the relative importance of temperature, DO and turbidity on predator habitat selection decisions and fish community composition. The model showed that DO had a stronger effect on community composition than temperature, and that reduced foraging success from high turbidity was able to overpower the other two factors. Hypoxia affects habitat selection decisions by fish species and can provide refuges from predation and competition, helping maintain higher species diversity. Water temperature appears to have a weaker effect on fish distributions than DO while turbidity primarily affects visual predators, though the strength of turbidity effects depends on the magnitude and duration of individual events.