Sex-specific maternal programming of corticosteroid-binding globulin by predator odour

Predation is a key organizing force in ecosystems. The threat of predation may act to programme the endocrine hypothalamic–pituitary–adrenal axis during development to prepare offspring for the environment they are likely to encounter. Such effects are typically investigated through the measurement of corticosteroids (Cort). Corticosteroid-binding globulin (CBG) plays a key role in regulating the bioavailability of Cort, with only free unbound Cort being biologically active. We investigated the effects of prenatal predator odour exposure (POE) in mice on offspring CBG and its impact on Cort dynamics before, during and after restraint stress in adulthood. POE males, but not females, had significantly higher serum CBG at baseline and during restraint and lower circulating levels of Free Cort. Restraint stress was associated with reduced liver transcript abundance of SerpinA6 (CBG-encoding gene) only in control males. POE did not affect SerpinA6 promoter DNA methylation. Our results indicate that prenatal exposure to a natural stressor led to increased CBG levels, decreased per cent of Free Cort relative to total and inhibited restraint stress-induced downregulation of CBG transcription. These changes suggest an adaptive response to a high predator risk environment in males but not females that could buffer male offspring from chronic Cort exposure.

Predicting multi-predator risk to elk (Cervus canadensis) using scats: Are migrant elk exposed to different predation risk?

There is evidence that prey can perceive the risk of predation and alter their behaviour in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk quantify predator space use to estimate potential predator-prey encounters, yet this approach does not account for successful predator attacks resulting in prey mortality. An exception is a prey kill-site, which reflects an encounter resulting in mortality, but obtaining these data can be expensive and requires time to accumulate adequate sample sizes. We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in Alberta, Canada. We combined predictions of scat-based resource selection functions for bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) based on scat-detection dog surveys with predictions for the probability that a predator-specific scat in a location contained elk. We evaluated our approach by comparing predictions to a predation risk model developed from elk kill sites and applied it to describing spatial patterns in predation risk that were consistent with changes in the distribution of elk over the past decade. We found a strong correlation between risk predicted by kill sites and risk predicted by our approach (r = 0.98, P < 0.001). There was a spatial pattern to predation risk, where elk that migrated east of their winter range were exposed to highest risk from cougars, non-migratory elk were exposed to high risk from wolves and bears, and risk to elk that migrated west of their winter range into protected areas was high only from bears. The patterns in predator risk were consistent with changes in the migratory tactics in this population. The scat-based approach we present permits broad-scale inferences on predation risk for prey.

Predicting multi-predator risk to elk (Cervus canadensis) using scats: Are migrant elk exposed to different predation risk?

There is evidence that prey can perceive the risk of predation and alter their behaviour in response, resulting in changes in spatial distribution and potential fitness consequences. Previous approaches to mapping predation risk quantify predator space use to estimate potential predator-prey encounters, yet this approach does not account for successful predator attacks resulting in prey mortality. An exception is a prey kill-site, which reflects an encounter resulting in mortality, but obtaining these data can be expensive and requires time to accumulate adequate sample sizes. We illustrate an alternative approach using predator scat locations and their contents to quantify spatial predation risk for elk (Cervus canadensis) from multiple predators in Alberta, Canada. We combined predictions of scat-based resource selection functions for bears (Ursus arctos/U. americanus), cougars (Puma concolor), coyotes (Canis latrans), and wolves (C. lupus) based on scat-detection dog surveys with predictions for the probability that a predator-specific scat in a location contained elk. We evaluated our approach by comparing predictions to a predation risk model developed from elk kill sites and applied it to describing spatial patterns in predation risk that were consistent with changes in the distribution of elk over the past decade. We found a strong correlation between risk predicted by kill sites and risk predicted by our approach (r = 0.98, P < 0.001). There was a spatial pattern to predation risk, where elk that migrated east of their winter range were exposed to highest risk from cougars, non-migratory elk were exposed to high risk from wolves and bears, and risk to elk that migrated west of their winter range into protected areas was high only from bears. The patterns in predator risk were consistent with changes in the migratory tactics in this population. The scat-based approach we present permits broad-scale inferences on predation risk for prey.

Predators affect a plant virus through direct and trait-mediated indirect effects on vectors

Arthropods that vector plant pathogens often interact with predators within food webs. Predators affect vectors by eating them (consumptive effects) and by inducing antipredator behaviors (non-consumptive effects), and these interactions may affect transmission of vector-borne pathogens. However, it has proven difficult to experimentally tease apart the effects of predators on vector fitness and behavior as they are often correlated. We addressed this problem by assessing how both aphids and an aphid-borne pathogen were affected by variable predation risk. Specifically, we experimentally manipulated ladybeetle predators’ mouthparts to isolate consumptive, and non-consumptive, effects of predators on aphid fitness, movement, and virus transmission. We show that although lethal predators decreased aphid vector abundance, they increased pathogen transmission by increasing aphid movement among hosts. Moreover, aphids responded to risk of predation by moving to younger plant tissue that was more susceptible to the pathogen. Aphids also responded to predator risk through compensatory reproduction, which offset direct consumptive effects. Our results support predictions of disease models showing alterations of vector movement due to predators can have greater effects on transmission of pathogens than vector consumption. Broadly, our study shows isolating direct and indirect predation effects can reveal novel pathways by which predators affect vector-borne pathogens.

Eggs, nests, and chicks

This chapter considers the egg from its conception, through laying and incubation, to hatching; and chicks. It begins with the genetic determination of sex in birds, the resultant secondary sexual characteristics, and associated reproductive behaviours. The chapter then considers the structure and function of the egg. The evolution of clutch size and the trade-offs related to food availability and predator risk that birds make when optimizing clutch size are discussed. Egg shell colouration, camouflage, and mimicry are explored as are the impacts of urban living and of anthropogenic pollution upon egg shell thickness and strength. Nest building and the function of nests are described and incubation behaviours are discussed. Embryonic development is considered as are hatching and post-hatching behaviours.

Foraging Behavior of Birds at Morning and Evening Times: A Preliminary Study

Birds exhibit a wide variety of behaviors including foraging behavior which could vary both inter- and intra-specifically. The current study was aimed to investigate different aspects of the foraging behavior of birds in different fields situated at the Quaid-e-Azam Campus, University of the Punjab, Lahore. The said campus covers an area of about 721 ha and has a stable ecosystem which supports a diverse range of birds. Three fields were selected for study purposes. The first field (F1) was characterized by dense vegetation. The second field (F2) contained relatively less vegetation and the third field (F3) was situated near the premises containing the hostel and the shopping center. Observations were recorded during December 2019 for a week at morning (0800-0900 h) and evening (1500-1600 h) times. The observations were based on the assumptions that an abundant availability of food will increase the stay time and vice versa. Moreover, number of pecks by birds also correlate with stay time. A total of 10, 8 and 5 bird species were observed in the above mentioned three fields, that is, F1, F2 and F3, respectively. Different patterns of bird frequency, pecking rate and search time were observed in all fields at morning and evening times which could be associated with the nature of the microhabitat, vegetation, predator risk, food availability, group size and various environmental factors such as temperature. Spearman’s correlation revealed a significant (p < 0.01) association between search time and number of pecks of birds in all three fields.

Behavioral adjustments to prior predation experience and food deprivation of a common cyprinid fish species vary between singletons and a group

Fish often undergo predation stress and food shortages in nature, and living in groups may provide the ecological benefits of decreased predator risk but the costs of increased food competition. The main aim of the present study was to test whether the behavioral response of qingbo (Spinibarbus sinensis) to predators and/or starvation differed between a singleton and a group. We measured the locomotor activity and distance to a predator and/or food item of prior predator-experienced, starved, double-treated and control qingbo; the qingbo were tested both as singletons and in a group (five individuals). Fish from all groups showed increased activity when tested collectively compared to individually. The predator-experienced fish showed decreased locomotor activity to predators as an antipredator strategy when tested as singletons; however, increased locomotor activity occurred when tested in a group, which might be partially due to the decreased predator risk when living in a group and thus higher levels of boldness. As expected, starvation elicited increased activity indicating increased foraging willingness when tested in a group; however, the difference between starved and normal-fed fish was no longer significant when they were tested as singletons, possibly due to the increased predation risk and decreased food competition when living individually and higher behavioral variation among individual fish than among those in a shoal. Compared with the control fish, the double-treated fish showed no difference in activity when tested both individually and collectively (except a slower speed when tested in a group). The reason for the results from the singletons might be an offset of the effect of predator exposure and starvation. The reason for this difference in the group might be due to the impaired body condition indicated by a slower swimming speed as a consequence of severe stress. The present study demonstrated that behavioral adjustment was closely related to the size of the group, which might be due to differences in the predation risk and food competition.