The northern fur seal (NFS) population on the Pribilof Islands (PI) is currently declining while the population on the Commander Islands (CI which includes Bering and Medny Islands) is stable. The reasons for the different population trajectories remain unknown. Comparing differences in behavioral ecology and predation pressure between these two populations could provide an explanation. This study examined lactating NFS female behavior to determine: 1) summer foraging patterns (trip duration, trip direction, dive depth) of animals from two nearby rookeries on Bering Island, 2) winter migration from Medny and Bering Islands relative to patterns of ocean productivity, and 3) the potential impact of killer whale predation on population dynamics. Data were collected from 2003 to 2010 using visual observations and telemetry. Twenty-one satellite transmitters, 29 time-depth recorders and 17 geolocation recorders were deployed. Shore-based observations of killer whale predation and photo-identification were conducted near the CI rookeries in 19992010. During lactation, both mean foraging trip duration and mean maximum diving depth (3.4 plus/minus 1.3 days and 17.7 plus/minus 6.8 m, respectively) for NFS adult females (n = 28) did not significantly change among years. Although foraging areas of NFS from the two rookeries on Bering Island overlapped, the mean direction of travel from Severo-Zapadnoe rookery was significantly (p<0.01) different compared with Severnoe rookery. The foraging patterns suggested that these females had a reliable food source that did not change despite potential environmental changes or the effects of fisheries. During their winter migration, NFS females from the CI traveled to the Transition Zone Chlorophyll Front (32° N-42° N) in the North Pacific Ocean. Their winter migration routes and the location of overwinter foraging areas were positively correlated with high ocean productivity (near surface chlorophyll a concentration). Over 82 percent (n=17) of these females spent 38 months near the eastern coast of Hokkaido, Japan and followed the coastal high productivity areas on their way back to the CI. Transient killer whales in groups of 2-12 individuals were repeatedly observed preying mostly on NFS males during the summer. The simulation model showed little impact on population dynamics as long as male fur seals were the primary prey. However, if the number of killer whales increased or they changed their diet to include females and pups, then the NFS population on the CI could decline. The winter migration of NFS from CI and PI are similar. Lactating NFS from the PI exhibit greater summer foraging effort (longer average trip duration and bout duration; greater number of deep dives) compared with females from the CI.

A mesocosm experiment was conducted in Lake Eymir between June &ndash / September 2009 in order to elucidate the effects of water level changes and fish predation on periphyton growth and macroinvertebrates in semi-arid shallow lakes. Twenty four cylindrical enclosures, each with 1.2 m diameter, open to lake bottom and atmosphere, were placed at three different depths, i.e. 0.8 m (low water level, LW), 1.6 m (high water level, HW) and 2.3 m (however, data regarding the enclosures at 2.3 m were excluded in this study due to complications after fifth sampling) to simulate water level fluctuations. At each water level, four replicates were stocked with omnivorous&ndash / planktivorous fish (Tinca tinca and Alburnus escherichii) and the other four replicates were left fishless to observe the effect of fish predation. Ten shoots of submerged macrophytes (Potamogeton pectinatus) were planted and six polyethylene strips were hung in the water column in each enclosure to monitor macrophyte and periphyton growth. The mesocosms were sampled for physical, chemical and biological parameters weekly in the first month and fortnightly thereafter. Benthic macroinvertebrate samples were taken before the start, in the middle and at the end of the experiment with Kajak corer. Macrophytes were harvested after the last sampling for determination of dry weight, epiphyton, and the associated macroinvertebrates. All macroinvertebrate samples were sieved through 212 &mu / m mesh size before identification and counting. Over the course of the experiment, an average of 0.46 &plusmn / 0.03 m water level decrease in the mesocosms triggered submerged macrophyte growth in all LW enclosures, overriding the negative effects of fish predation. The results indicate that while fish predation pressure had negative influences on macroinvertebrate communities in terms of both abundance and richness, structural complexity created by dense vegetation in the LW mesocosms weakened the top-down effect of fish on macroinvertebrates by acting as a refuge in this semi-arid shallow lake.

This study seeks to identify naturally occurring differences in the turbulent environment at a variety of field sites near the Skidaway Institute of Oceanography, in Wassaw Sound and surrounding bodies of water. The sites have previously been used to study predator-prey interactions. Velocity time records were recorded using acoustic Doppler velocimetry (ADV) probes at six sites on four days, with a total of 14 data sets. Differential estimate phase filtering was employed to identify erroneous velocity measurements. Less than 3% of the total samples were identified for any given data set with the exception of three sets that contained nonphysical banded bursts. Set mean velocity statistics were largely unaffected by phase filtration, while turbulent kinetic energy (TKE) was reduced in magnitude. Because the sites were exposed to waves, wave contributions to TKE and Reynolds shear stress were computed. Power spectral densities (PSDs) were computed for each velocity burst, and the contributions from wave-related and turbulent fluctuations were isolated. Wave components of TKE and Reynolds shear stress were computed. Wave contributions to turbulent characteristics for most sets were between 10-20% of the total value. Wave contributions to TKE were consistent but wave contributions to Reynolds shear stresses were irregular. Burst-average velocity statistics, TKE, Reynolds shear stress, and turbulence intensity (TI) were computed for each set. Large variability in turbulent characteristics was observed both temporally and spatially. Tidal influences were apparent as turbulent characteristics often reached absolute maximum values during the incoming or outgoing tides. No consistent trends were observed in relationships between the sites. The findings of the study emphasize the importance of applying data filtration to raw ADV data, suggest an order of magnitude of wave contributions in a particular tidal ecosystem, and demonstrate the inherent variability of turbulent characteristics. The study also illustrates the importance of considering multiple turbulence parameters for a give site, due to the lack of observed relationships between TKE, TI, and Reynolds shear stress. Further work is needed to determine if other parameters that are relevant from a flow characterization standpoint are also important ecologically.

The focus of this study was to determine the effect of clam presence and behavior on the crossflow of the ambient horizontal flow and the effect of ambient horizontal flow characteristics influence the clam feeding behavior. Hence, there is a reciprocal relationship between organisms and the physical environment, and this study ultimately addressed the role of hydrodynamics in the predator-prey relationship between bivalve clams, Mercenaria mercenaria, and their predators, blue crabs and whelks. The study concludes that clams alter the chemical odorant source characteristics and control the transmission of the chemical signal through altering the crossflow. The first part of the study is a field experiment designed to quantify the effect of the presence and behavior of clams on the crossflow of the horizontal crossflow. The second part of this study is a two-part laboratory experiment designed to isolate the influence of environmental factors on clam behavior. One experiment quantifies the unsteadiness of the clam excurrent jet velocity time record according to environmental cues such as the horizontal crossflow velocity, the density of the clam patch, and the size of the clam. The second laboratory experiment quantifies the unsteadiness of the jet velocity values according to the presence of predator cues in the upstream flow. Clams are found, using an ADV system in the field, to alter the vertical distribution of velocity according to the sediment in which they are buried. Also, turbulence characteristics, such as Turbulent Kinetic Energy and Reynolds shear stress, are altered in the presence of clams according to the ambient horizontal crossflow velocity and treatment site. The laboratory flume PIV system captured vector plots for two-dimensional planes that bisect the clam excurrent siphons and clam jet velocity time records were extracted. A fractal analysis and a lacunarity analysis of the jet velocity time records found that clams alter their jet excurrent velocity unsteadiness according to the horizontal crossflow velocity. This behavioral change may contribute to the differences in the turbulence characteristics in the field experiment. Another result from the laboratory experiments is that the effect of clam patch density on the feeding activity was dependent on the size of the organism. This size/density dependent relationship suggests that predation by blue crabs dominates the system since larger clams are no longer susceptible to blue crab predation, whereas clams of all sizes are susceptible to whelk predation. Finally, clams increase the randomness of their excurrent jet velocity values when predator cues are located in the upstream flume flow. This suggests that the presence of predators elicits clam behavior that promotes the mixing and dilution of their chemical metabolites.

Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009. / Committee Chair: Weiss, Howard; Committee Member: Cvitanovic , Predrag; Committee Member: Goldman, Daniel; Committee Member: Schatz, Michael; Committee Member: Wiesenfeld, Kurt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The complex interaction between predators and their prey is rarely preserved in the fossil record. However, predation of marine mollusks by drilling gastropods leaves a diagnostic hole in the shell of the prey, possibly allowing for quantitative analysis of this ecological interaction. Drilling frequency, as measured in marine mollusks both in the Modern and fossil record, has been heralded as a potential opportunity to quantify these ecological interactions and use these values in the testing of hypotheses. This study employed the collection, tallying, and analysis of bulk samples derived from shelly deposits on 45 Modern beaches along the contiguous coast of the southeast United States (Virginia Beach, VA to Port Isabella, TX). The tallying scheme allowed for pooling and reduction of the data to compare drilling frequencies at several taxonomic and geographic scales. In addition, multivariate clustering analyses was used to generate groups of similar taxonomic abundances for direct comparison. Understanding potential spatial variation in the natural environment is paramount to using quantified values of drilling frequency in temporal and spatial studies in the fossil record. Calculated drilling frequencies for bulk (location) samples ranged from 0 to over 100%. Similar ranges of drilling frequency were observed in more finely defined taxonomic groups. Calculated drilling frequency was higher in the Carolinian province as compared to the Gulf-Louisianian and Virginian provinces. No correlation between drilling frequency and latitude was observed at any scale. An area of substantially increased drilling frequency was observed along the Carolina coast, at the ecotone between the Carolinian and Virginian provinces, suggesting that some environmental condition is present and responsible for the local increase in drilling frequency. Finally, little attention has been paid to sampling techniques and their subsequent impact on the analysis of drilling frequency. As the bulk samples represent aggregate accumulations of shells from a myriad of environments, this introduces pronounced variation in the analysis that has not been previously accounted for. Statistically, much larger abundances of specimens in individual taxa, approaching 450 values for bivalves, are needed to effectively constrain this variability.

The invasive cactus moth, Cactoblastis cactorum, poses a threat to opunitoid cacti species of North America. The following work contains four separate studies investigating C. cactorum host plant preference and performance, predation and parastitism of C. cactorum, effects of C. cactorum on local Opuntia populations, and associational effects of host and non-host plants on C. cactorum and native Opuntia-feeding herbivores. We found that, among southwestern and Mexican opuntioid taxa, moths preferred O. engelmannii var. linguiformis and var. engelmannii for oviposition, while Consolea rubescens and O. streptacantha were superior larval hosts. Oviposition was best predicted by number of cladodes and degree of spininess; epidermal toughness was a significant predictor of most larval fitness parameters. In general, oviposition preference was not correlated with larval performance. A lack of co-evolutionary history between C. cactorum and North American opuntioid species may help explain this disconnect. We placed irradiated C. cactorum eggsticks and pupae on Opuntia plants in the field to test for predation. We found evidence of predation, most likely from ants, on ~16% of eggsticks and ~18% of pupae. Predation rates, ant abundance, and cladode growth were higher, and C. cactorum damage lower, on Opuntia located near the extrafloral nectar-producing legume Chamaecrista fasciculata. We attribute these associational effects to the ability of C. fasciculata to attract ants to its extrafloral nectar. Over the course of six years, ~78% of nearly 600 tagged Opuntia were attacked by C. cactorum at least once and ~76% of the plants survived. Two separate studies found that Opuntia stricta was more likely to be attacked by C. cactorum than O. humifusa; we also found that O. stricta was more likely to die following an attack. A plant's odds of survival decreased as C. cactorum attack frequency increased, but plants that did survive had positive growth rates, regardless of attack status. We did not find significant evidence of associational effects for O. humifusa and O. stricta, either for C. cactorum or native Opuntia-feeding herbivores. It could be that present herbivore densities are low enough, and host plants plentiful enough, to avoid mechanisms that usually lead to associational resistance or susceptibility. Overall, our results suggest that the presence and spread of C. cactorum should be taken seriously, especially for rare opuntioids and the Opuntia-rich deserts of North America. However, for more common opuntioid host species, there may be enough resistant or tolerant individuals, and sufficient top down control through ant predation, for populations to persist at current C. cactorum densities. We acknowledge that information on Opuntia reproduction and recruitment rates are needed to confirm this suggestion, and see this as an excellent opportunity for future research

Studies of secondary seed dispersal by small mammals have largely been focused on the interaction between nut-bearing tree species and sciurid rodents such as squirrels, and on heteromyid rodents in the southwestern United States. However, there is now evidence that wind-dispersed tree species such as pines also undergo a process of secondary seed dispersal, where animals redistribute (cache) seeds that have already fallen to the ground, often in microhabitats more suitable for successful seed germination. In Florida sandhill, where fire suppression has threatened wind-dispersed longleaf pine ( Pinus palustris) by encouraging the encroachment of hardwoods such as sand live oak ( Quercus geminata), secondary seed dispersal may be an important factor in determining community composition and persistence of longleaf pine systems. Using a combination of seed depots and seed predator exclosures, I looked at both longleaf pine and sand live oak in terms of whether small animals such as squirrels ( Sciurus carolinensis) and cotton mice ( Peromyscus gossypinus) cache the seeds, and where the seeds of these two tree species best germinate. Since sand live oak acorns are prone to infestation by weevils ( Curculio spp.), I also examined whether nut condition affects acorn germination potential. I found that longleaf pine seeds are cached by small mammals to a small degree. While these seeds are not moved great distances from where they originate, they are often redistributed into microhabitats that promote successful seed germination. Caging experiments indicated that seeds were most likely to germinate when buried in open areas between adult trees, and to some degree, under shrub cover. On the other hand, sand live oak acorns appear to face heavy predation by large seed predators such as raccoons ( Procyon lotor) and wild pigs (Sus scrofa). Those acorns that do escape predation, including weevil-infested acorns, may provide an opportunity for seedling establishment. However, it appears that sand live oak depends heavily on vegetative sprouting for regeneration. This suggests that even in the absence of fire, longleaf pines in Florida sandhill are able to persist through secondary seed dispersal by small animals coupled with heavy seed predation on competing sand live oak.

Social parasitism, the exploitation of a society by other social organisms, has evolved independently numerous times within social animals. In this thesis, I integrate behavioral, evolutionary and chemical analyses to elucidate the evolution of social parasitism in Megalomyrmex ants. I examine host-parasite interactions in two Megalomyrmex species, identify venom alkaloids, and reconstruct the phylogenetic relationships between species. In Chapter 1, I analyze nest architecture and behavioral interactions between the ant host Cyphomyrmex cornutus and its parasite Megalomyrmex mondabora. This is the first detailed account of the natural history of this host and its social parasite. In Chapter 2, I report a one-year-long fitness experiment that tests whether Trachymyrmex cf. zeteki colonies suffer reduced fitness from an association with the social parasite Megalomyrmex symmetochus. I show that M. symmetochus parasites negatively impact host fitness though several mechanisms, including a) manipulation of the host worker grooming behavior; b) castration of host queens produced by the host colony, which then become workers; and c) reduction of garden size, host worker number, and host reproductive output. In Chapter 3, I determine that five venom alkaloids of Megalomyrmex are taxonomically informative to help differentiate cryptic species within the M. mondabora complex; new species in this complex need to be described in a future taxonomic revision. In Chapter 4, I reconstruct phylogenetic relationships of the genus Megalomyrmex with DNA sequence information. I conclude that the genus is monophyletic and corroborate two of the four species groups proposed by Brandão (1990) in a previous morphological revision. I also find evidence in support of Darwin’s Predation Hypothesis on the origin of social parasitism, which postulates that socialparasitic behaviors evolve from predatory behaviors. Lastly, I discuss promising future research directions on the evolution of social parasitism in the ant genus Megalomyrmex, which could serve as a model for the study of social parasitism in other lineages of social insects. / text

Previous studies have shown that ice cover has many positive effects on brown trout (Salmo trutta), including protection from endothermic predators. I tested whether it is the cover provided by the ice itself or the reduction in light that causes behavioral changes in juvenile brown trout. To distinguish between these two effects, behavioural observations were made with and without ice at the same light intensity (500 lux). An additional ice-free, high light (3000 lux) treatment was included to be able to measure brown trout’s response to light reduction. A mink model was used to simulate predation risk to be able to measure the fish’s anti-predator response under these three conditions. I found a significant treatment effect on body and eye coloruration. For eye colouration, I found that fish under ice had a paler eye colouration than fish that experienced high light, which in turn were paler than fish subjected to low light. For body colouration, fish under ice had paler body colouration than fish from the two ice-free treatments, which did not differ from each other. There was no effect of treatment on ventilation rate, time to initiate foraging, time to initiate activity or swimming activity, although both foraging and activity were lowest and swimming activity highest under ice. The changes in body and eye colouration indicate that trout are less stressed under ice, presumably because they perceive ice as a barrier against terrestrial predators. These results suggest that the ongoing climate change, which is leading to shorter periods of sustained ice cover, may have negative consequences for trout populations in the near future. / Tidigare studier har visat att yttäckande is medför många positiva effekter för öring (Salmo trutta), bland annat genom att utgöra skydd mot endoterma predatorer. Jag undersökte om det är den yttäckande isen i sig som medför beteendeförändringar hos juvenila öringar eller om det är det reducerade ljusinsläppet som isen medför. För att separera dessa två effekter gjordes beteendeobservationer med och utan ytis under samma ljusintensitet (500 lux). En ytterligare isfri behandling gjordes, med starkt ljus (3000 lux), för att kunna mäta öringens respons på ljusreduceringen. En uppstoppad mink användes för att simulera predationsrisken, detta för att kunna mäta fiskarnas antipredationsresponser under dessa tre förhållanden. Jag fann en signifikant behandlingseffekt på kropps- och ögonfärg. Under is hade fiskarna en blekare ögonfärg än när de befann sig under starkt ljus, som i sin tur resulterade i blekare färg än när fiskarna utsattes för svagt ljus. När det gäller kroppsfärg uppvisade fiskarna en blekare kroppsfärg under is än när de utsattes för de två isfria behandlingarna, vilka inte skiljde sig från varandra. Behandlingarna gav ingen effekt på gälslagsfrekvens, tid till att initiera födosök, tid till att initiera aktivitet eller simaktivitet, dock var tid till både födosök och aktivitet lägst och simaktivitet störst under is. Förändringarna i kropps- och ögonfärg indikerar att öring är mindre stressad under is, vilket eventuellt kan bero på att de uppfattar isen som en barriär mot terrestra predatorer. Dessa resultat tyder på att den pågående klimatförändringen, som innebär kortare perioder av ihållande yttäckande is, kan medföra negativa konsekvenser för öringpopulationer inom den närmaste framtiden.