Pest Responses to Odors From Predators Fed a Diet of Target Species Conspecifics and Heterospecifics

ABSTRACT Research into the use of predator-odor-based repellents as a management tool has gained momentum during the past 30 years. Some studies have suggested that odors from a predator whose diet includes the target species are more effective than odors from a predator that does not consume the species. To evaluate this management tool in the Australian context and to determine the effect, if any, of predator diet on odor repellence, we tested eutherian and metatherian, predator fecal odors on phylogenetically separated pest species that currently occur in Australia. We evaluated fecal odors from tigers (Panthera tigris) and Tasmanian devils (Sarcophilus harrisii) as repellents for goats (Capra hircus) and eastern grey kangaroos (Macropus giganteus). We fed tigers and Tasmanian devils 2 diets: one of goat and one of eastern grey kangaroo. The test fecal odors were more effective than a control odor of carrier material and solvent at deterring goats (P < 0.001) and kangaroos (P = 0.02) from food. Tiger fecal odor was more effective than Tasmanian devil odor in deterring both goats (P = 0.001)and kangaroos (P = 0.03). We observed a decrease in the number of feeding events for goats when they were exposed to the odor from a tiger fed goat compared with all other predator-diet combinations (P < 0.001). We also observed a decrease in feeding events for kangaroos when exposed to the odor from a tiger fed kangaroo compared with all other predator-diet combinations. We observed signs of desensitization to the test odors in goats and habituation to the test odors in kangaroos over the experimental period. A better understanding of the factors involved in desensitization and habituation may increase the effectiveness of fecal odor-based repellents as a humane and nonlethal management tool for managers.     

Influence of Different Individual Traits on Vigilance Behaviour in European Rabbits

An animal's level of vigilance depends on various environmental factors such as predator presence or the proximity of conspecific competitors. In addition, several individual traits may influence vigilance. We investigated the effects of body condition, social rank and the state of pregnancy on individual vigilance (scanning) rates in individually marked European rabbits ( Oryctolagus cuniculus ) of a field enclosure population. We found lower rates in young rabbits than in adult females, but male and female juveniles did not differ. Vigilance of juveniles was positively correlated with their age-dependent body mass (used as a measure of body condition), i.e. young rabbits with lower body condition scanned less. We suggest that juveniles with low body condition were trading off vigilance against feeding to maximise their growth. In contrast, there was no significant correlation between body mass and vigilance in adult females. Adult females increased scanning rates during late pregnancy, which might constitute a behavioural compensation because of their lower capacity to escape predator attacks. In addition, adult females with low social ranks scanned more than high ranking individuals, likely because of their higher risk of attacks by conspecifics. In summary, our results highlight various individual characteristics that influence vigilance behaviour in European rabbits.     

Vigilance and Collective Detection of Predators in Degus (Octodon degus)

Individuals of social and partially social species typically reduce their vigilance activity when foraging in groups. As a result, per capita risk of predation decreases and individuals allocate more time to foraging and other fitness rewarding activities. Reduction of per capita risk is hypothesized to occur because there are more individuals to detect potential predators. If so, collective (i.e. total) vigilance is expected to increase with foraging group size. Increased surveillance during group foraging may occur if group members scan independently of one another, or sequentially to avoid the overlapping of their vigilance bouts. Intriguingly, such coordinated vigilance assumes that individuals monitor not only the presence, but the vigilance behaviour of group mates. We used seasonal records on time budget and grouping patterns of individually marked degus (Octodon degus), a social rodent, to examine if (a) individual vigilance decreases and/or foraging increases with group size, (b) collective vigilance increases with group size and (c) foraging degus coordinate their vigilance. When foraging, degus decreased their individual vigilance and increased their foraging time when in larger groups. Despite this, degus in larger groups increased their collective vigilance, supporting the hypothesis that socially foraging degus decrease predation risk through an improved ability to detect and escape potential predators. Additionally, patterns of collective vigilance suggested that degus scan independently of each other and so, they do not coordinate their vigilance to prevent its temporal overlapping. This finding does not support that foraging degus monitor the vigilance activity of group mates.     

Fine-Scale Genetic Response to Landscape Change in a Gliding Mammal

Understanding how populations respond to habitat loss is central to conserving biodiversity. Population genetic approaches enable the identification of the symptoms of population disruption in advance of population collapse. However, the spatio-temporal scales at which population disruption occurs are still too poorly known to effectively conserve biodiversity in the face of human-induced landscape change. We employed microsatellite analysis to examine genetic structure and diversity over small spatial (mostly 1-50 km) and temporal scales (20-50 years) in the squirrel glider (Petaurus norfolcensis), a gliding mammal that is commonly subjected to a loss of habitat connectivity. We identified genetically differentiated local populations over distances as little as 3 km and within 30 years of landscape change. Genetically isolated local populations experienced the loss of genetic diversity, and significantly increased mean relatedness, which suggests increased inbreeding. Where tree cover remained, genetic differentiation was less evident. This pattern was repeated in two landscapes located 750 km apart. These results lend support to other recent studies that suggest the loss of habitat connectivity can produce fine-scale population genetic change in a range of taxa. This gives rise to the prediction that many other vertebrates will experience similar genetic changes. Our results suggest the future collapse of local populations of this gliding mammal is likely unless habitat connectivity is maintained or restored. Landscape management must occur on a fine-scale to avert the erosion of biodiversity.     

Recognition and Response to Native and Novel Predators in the Largespring mosquitofish,Gambusia geiseri

The introduction of predator species into new habitats is an increasingly common consequence of human activities, and the persistence of native prey species depends upon their response to these novel predators. In this study, we examined whether the Largespring mosquitofish, Gambusia geiseri exhibited antipredator behavior and/or an elevation of circulating stress hormones (cortisol) to visual and chemical cues from a native predator, a novel predator, or a non‐predatory control fish. Prey showed the most pronounced antipredator response to the native predator treatment, by moving away from the stimulus, while the prey showed no significant changes in their vertical or horizontal position in response to the novel or non‐predator treatments. We also found no significant difference in water‐borne cortisol release rates following any of the treatments. Our results suggest the prey did not recognize and exhibit antipredator behavior to the novel predator, and we infer that this predator species could be detrimental if it expands into the range of this prey species. Further, our study demonstrates prey may not respond to an invasive predator that is phylogenetically, behaviorally, and morphologically dissimilar from the prey species' native predators.     

Space Use in Response to Conspecifics by the Red-backed Salamander (Plethodon cinereus, Plethodontidae, Caudata)

The presence of conspecifics, as well as the distribution and quality of resources, can influence habitat settlement decisions of animals. We studied the habitat preference and group size of the red-backed salamander, Plethodon cinereus , from the Upper Peninsula of Michigan. In contrast to previous work with P. cinereus from Virginia, we found groups of P. cinereus within higher quality habitat than solitary individuals and these groups contained both small and large individuals. Under identical conditions in the laboratory, salamanders from Virginia formed a uniform spatial distribution and individuals from northern Michigan displayed an aggregated spatial distribution. Our results suggest that P. cinereus from northern Michigan preferentially settle near conspecifics, while P. cinereus from Virginia avoid them. Our laboratory experiments also suggest that the aggregation behaviour of P. cinereus from northern Michigan may be the result of attraction to conspecifics rather than attraction to habitat features.     

Testing Broadcast Seeding Methods to Restore Urban Forests in the Presence of Seed Predators

Forest restoration in urban areas often occurs in isolation from remnant forest, limiting the chances for recolonization by native species. Plants with bird‐dispersed seeds can be particularly vulnerable to dispersal limitation and regeneration can be further impeded by non‐native seed predators. We used a factorial experiment to investigate broadcast seeding as a method to reintroduce trees with large seeds and fleshy fruits into early successional forests. We assessed rates of seed and fruit loss, germination and seedling establishment in three seed treatments: (1) caging to exclude introduced mammalian seed predators; (2) removal of fleshy fruit pericarp; and (3) placing seeds in nutritionally enriched clay balls. Across all species (Beilschmiedia tawa, Elaeocarpus dentatus, and Litsea calicaris) seeds and fruits accessible to mammalian predators suffered significantly greater loss (58%) than those protected by cages (4%). However, seed and fruit loss in the presence of predators was reduced to only 35% across all species by the treatment combining the removal of fruit flesh and clay ball application to seeds. Establishment of B. tawa seedlings after 1 year was significantly enhanced by the clay ball treatment (12% of seeds sown vs. 6% without clay balls). Very low establishment rates were recorded for E. dentatus and L. calicaris. Broadcast seeding was found to be a viable method of improving regeneration of large‐seeded late successional trees and may be a cost‐effective alternative to planting saplings. Seedling establishment can be improved with fruit flesh removal and clay ball treatments, especially in the presence of mammalian seed predators.     

Linking Morphological and Behavioural Defences: Prey Fish Detect the Morphology of Conspecifics in the Odour Signature of their Predators

Predation is a strong selective force acting on both morphology and behaviour of prey animals. While morphological defences (e.g. crypsis, presence of armours or spines or specific body morphologies) and antipredator behaviours (e.g. change in foraging or reproductive effort, or hiding and fleeing behaviours) have been widely studied separately, few studies have considered the interplay between the two. The question raised in our study is whether antipredator behaviours of a prey fish to predator odours could be influenced by the morphology of prey conspecifics in the diet of the predator. We used goldfish (Carassius auratus) as our test species; goldfish exposed to predation risk significantly increase their body depth to length ratio, which gives them a survival advantage against gape‐limited predators. We exposed shallow‐bodied and deep‐bodied goldfish to the odour of pike (Esox lucius) fed either form of goldfish. Deep‐bodied goldfish displayed lower intensity antipredator responses than shallow‐bodied ones, consistent with the hypothesis that individuals with morphological defences should exhibit less behavioural modification than those lacking such defences. Moreover, both shallow‐ and deep‐bodied goldfish displayed their strongest antipredator responses when exposed to the odour of pike fed conspecifics of their own morphology, indicating that goldfish are able to differentiate the morphology of conspecifics through predator diet cues. For a given individual, predator threat increases as the prey become more like the individual eaten, revealing a surprising level of sophistication of chemosensory assessment by prey fish.     

Protozoan Response to the Addition of Bacterial Predators and Other Bacteria to Soil

Representatives of several categories of bacteria were added to soil to determine which of them might elicit responses from the soil protozoa. The various categories were nonobligate bacterial predators of bacteria, prey bacteria for these predators, indigenous bacteria that are normally present in high numbers in soil, and non-native bacteria that often find their way in large numbers into soil. The soil was incubated and the responses of the indigenous protozoa were determined by most-probable-number estimations of total numbers of protozoa. Although each soil was incubated with only one species of added bacteria, the protozoan response for the soil was evaluated by using most-probable-number estimations of several species of bacteria. The protozoa did not respond to incubation of the soil with either Cupriavidus necator, a potent bacterial predator, or one of its prey species, Micrococcus luteus. C. necator also had no effect on the protozoa. Therefore, in this case, bacterial and protozoan predators did not interact, except for possible competition for bacterial prey cells. The soil protozoa did not respond to the addition of Arthrobacter globiformis or Bacillus thuringiensis. Therefore, the autochthonous state of Arthrobacter species in soil and the survival of B. thuringiensis were possibly enhanced by the resistance of these species to protozoa. The addition of Bacillus mycoides and Escherichia coli cells caused specific responses by soil protozoa. The protozoa that responded to E. coli did not respond to B. mycoides or any other bacteria, and vice versa. Therefore, addition to soil of a nonsoil bacterium, such as E. coli, did not cause a general increase in numbers of protozoa or in protozoan control of the activities of other bacteria in the soil.     

斜生栅藻对不同形态锑胁迫的响应及抗性研究

该研究以斜生栅藻(Scenedesmus obliquus)为研究对象,研究不同浓度的Sb(Ⅲ)、Sb(Ⅴ)胁迫下对斜生栅藻生长速率、叶绿素a、抗氧化酶活性和细胞表面结构的影响,以探讨重金属胁迫下斜生栅藻的抗性机理。结果表明:(1)在高浓度Sb(Ⅲ)、Sb(Ⅴ)胁迫处理中,斜生栅藻生长对Sb(Ⅲ)胁迫的响应更加迅速;随着Sb(Ⅲ)、Sb(Ⅴ)胁迫浓度增加,斜生栅藻体内叶绿素a含量呈下降趋势,且对Sb(Ⅲ)胁迫浓度的变化反应更为敏感。(2)在800μmol/L Sb(Ⅲ)和Sb(Ⅴ)胁迫下,斜生栅藻体内丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性分别在胁迫第7~8天和第6~7天时变化更为明显;过氧化氢酶(CAT)活性在胁迫处理的第4~5天就迅速增加,对Sb胁迫响应比SOD更为迅速。(3)在高浓度Sb(Ⅲ)、Sb(Ⅴ)胁迫下,斜生栅藻细胞结构受到严重损伤,而且Sb(Ⅲ)对斜生栅藻细胞的损伤更加明显。研究发现,Sb(Ⅲ)、Sb(Ⅴ)对斜生栅藻生长、叶绿素a及细胞结构表现出不同程度的抑制和破坏作用,其细胞受到的影响程度与Sb(Ⅲ)、Sb(Ⅴ)的处理浓度及处理时间均密切相关,但斜生栅藻依靠自身抗氧化酶系统在一定程度上能够缓解Sb胁迫的不利影响。     

Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change

Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC) in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ). This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500–8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population ~8,000 YBP, followed by directional migration away from VLC and the loss of diversity at ~1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, ~7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available.     

Minimal Number of Conspecifics Needed to Minimize the Stress Response of Isolated Mature Ewes

The objective of this study was to determine the minimum number of conspecifics that sheep require to minimize the stress associated with isolation from the flock. The study used twelve 3-year-old Suffolk ewes. Every test day the study randomly chose 1, 2, or 3 ewes to be visually separated from the flock for 20 min in a familiar pen, 20 m distance from their original pen. One of the ewes that remained in the flock was randomly chosen as a control. The dependent variables measured were number of steps, serum cortisol levels, body temperature, and heart and respiration rates before and after the 20 min isolation test. The study also recorded number of vocalizations and urinations. Results show that individual separation induced significant increases in respiration rate (p < .01), serum cortisol concentration (p < .01), number of steps (p < .01), vocalizations (p < .01), and urinations (p < .05). This effect declined to basal levels (control ewes) when a single companion ewe was present. There were no additionally significant (p > .05) advantages to having 2 companion ewes. The results indicate that the welfare of ewes is improved if they are separated from the flock in groups of at least 2 members.     

Two's a Crowd: Phenotypic Adjustments and Prophylaxis in Anticarsia gemmatalis Larvae Are Triggered by the Presence of Conspecifics

Defence from parasites and pathogens involves a cost. Thus, it is expected that organisms use this only at high population densities, where the risk of pathogen transmission may be high, as proposed by the "density-dependent prophylaxis" (DDP) hypothesis. These predictions have been tested in a wide range of insects, both in comparative and experimental studies. We think it pertinent to consider a continuum between solitarious and gregarious living insects, wherein: (1) solitarious insects are those that are constitutively solitary and do not express any phenotypic plasticity, (2) the middle of the continuum is represented by insects that are subject to fluctuations in local density and show a range of facultative and plastic changes; and (3) constitutively gregarious forms live gregariously and show the gregarious phenotype even in the absence of crowding stimuli. We aimed to chart some of the intermediary continuum with an insect that presents solitarious aspects, but that is subject to fluctuations in density. Thus, Anticarsia gemmatalis (Lepidoptera: Noctuidae) larvae reared at higher densities showed changes in coloration, a greater degree of encapsulation, had higher hemocyte densities and were more resistant to Baculovirus anticarsia, but not to Bacillus thuringiensis. Meanwhile, with increased rearing density there was reduced capsule melanization. Hemocyte density was the only variable that did not vary according to larval phenotype. The observed responses were not a continuous function of larval density, but an all-or-nothing response to the presence of a conspecific. As A. gemmatalis is not known for gregarious living, yet shows these density-dependent changes, it thus seems that this plastic phenotypic adjustment may be a broader phenomenon than previously thought.     

Immunological Response of the Rabbit to Vi Antigen

Vi antibody response of rabbits varied depending on whether Vi antigen was administered in particulate or soluble state. Vi antigen in particulate form induced hemagglutinins, bacterial agglutinins, and passive cutaneous anaphylaxis (PCA) antibodies, whereas soluble Vi antigen induced only hemagglutinins. Guinea pigs passively sensitized with antisera against particulate Vi antigen gave PCA reactions when challenged with either soluble or cellular Vi antigen; antisera against soluble Vi antigen were negative for PCA. The specificity of PCA was demonstrated by its dependence on the Vi concentration and by absorption of PCA activity from antisera with V-form cells of Salmonella typhosa.     

Optimal Mating Strategies for Preferentially Outcrossing Simultaneous Hermaphrodites in the Presence of Predators

The optimal timing for initiating reproduction (i.e., the age at first reproduction) is a critical life history trait describing aspects of an individual’s resource-allocation strategy. Recent theoretical and empirical work has demonstrated that this trait is also tied to mating system expression when individuals have the opportunity to reproduce via both self-fertilization and cross-fertilization. A strategy of “delayed selfing” has emerged as a “best of both worlds” arrangement where, in the absence of a mate, an individual will delay reproduction (selfing) to “wait” for a mate. Herein, we extend previously developed predictive optimization models for the timing of reproduction to a situation where organisms can allocate their resources to size-dependent and size-independent defensive strategies to counter the threat of predation. By incorporating inducible defenses into a predictive framework for analyzing life history expression and evolution, we can more accurately evaluate the role that allocation strategy plays in altering the optimal waiting time. We compare our model to previous models and empirical results highlighting that incorporation of inducible defenses into the model broadens the parameter space in which a waiting time is expected and often leads to a predicted waiting time that is longer than in the situation without inducible defenses. In particular, a waiting time is predicted to exist regardless of the strength of inbreeding depression in the population.     

The Repair Response to Osteochondral Implant Types in a Rabbit Model

Current treatments for damaged articular cartilage (i.e., shaving the articular surface, perforation or abrasion of the subchondral bone, and resurfacing with periosteal and perichondrial resurfacing) often produce fibrocartilage, or hyaline-appearing repair that is not sustained over time (Henche 1967, Ligament and Articular Cartilage Injuries. Springer-Verlag, New York, NY, pp. 157–164; Insall 1974, Clin. Orthop. 101: 61–67; Mitchell and Shepard 1976, J. Bone Joint Surg. [Am.] 58: 230–233; O’Driscoll et al. 1986, J. Bone Joint Surg. [Am.] 68: 1017–1035; 1989, Trans. Orthop. Res. Soc. 14: 145; Kim et al. 1991, J. Bone Joint Surg. [Am.] 73: 1301–1315). Autologous chondrocyte transplantation, although promising, requires two surgeries, has site-dependent and patient age limitations, and has unknown long-term donor site morbidity (Brittberg et al. 1994, N Engl. J. Med. 331: 889–895; Minas 2003, Orthopedics 26: 945–947; Peterson et al. 2003, J. Bone Joint Surg. Am. 85-A(Suppl. 2): S17–S24). Osteochondral allografts remain a widely used method of articular resurfacing to delay arthritic progression. The present study compared the histological response to four types of osteochondral implants in a rabbit model: autograft, frozen, freeze-dried, and fresh implants. Specimens implanted in the femoral groove were harvested at 6 and 12 weeks. Results showed similar restoration of the joint surface regardless of implant type, with a trend toward better repair at the later timepoint. As has been observed in other studies (Frenkel et al. 1997, J. Bone Joint Surg. 79B: 281–286; Toolan et al. 1998, J. Biomed. Mater. Res. 41: 244–250), each group in this study had at least one specimen in which a healthy-appearing surface on the implant was not well-integrated with host tissues. Although the differences were not statistically significant, freeze-dried implants at both timepoints had the best histological scores. The osteochondral grafts tested successfully restored the gross joint surface and congruity. At 12 weeks, no significant differences were observed between the various allografts and autologous osteochondral grafts.     

Vibrational Communication and the Ecology of Group-Living, Herbivorous Insects

Communication among members of a colony is a key feature ofthe success of eusocial insects. The same may be true in otherforms of insect sociality. I suggest that substrate-borne vibrationalcommunication is important in the success of group-living, herbivorousinsects. I examine three challenges encountered by herbivorousinsects: locating and remaining in a group of conspecifics;locating food resources; and avoiding predation. Studies ofgroups of immature treehoppers, sawflies and butterflies suggestthat vibrational communication can be important in each of thesecontexts, enhancing the ability of these group-living herbivoresto exploit the resources of their host plants.     

Presence of Different O Antigen Forms in Three Isolates of One Clone of Escherichia Coli

Escherichia coli strains ECOR2, ECOR3 and K-12 are very closely related in genotype as indicated by multilocus enzyme electrophoresis. We show that they have very different rfb regions indicating that recombination has occurred in this region, and we suggest that it may be associated with niche adaptation.