Adult tiger beetles Cicindela gemmata modify their foraging strategy in different hunting contexts

Predator–prey interaction has long been an interesting item in the research of animal behaviors.Given that live prey can damage their predators,predators must trade foraging efficiency for safety while hunting,but the extent of this trade-off is not yet clear.Tiger beetles display diversity in their diets and hunting strategies,and hence,they become an ideal system to address how self-security affects foraging efficiency.We addressed this question in captive adult tiger beetles Cicindela gemmata.By offering several types of arthropod and plant foods,we confirmed that C.gemmata is carnivorous.We found that C.gemmata hunt by either ambushing or chasing their prey,and that they switch between strategies based on differences in the number of prey,the prey status and encounter rate,and the number of predators.Ambushing success increased with the number of prey but decreased with prey encounter rate.Chasing success decreased as prey body size and encounter rate increased.Foraging Cicindela gemmata often gave up an attack when it was nonfatal.This active giving up of hunting may be a consequence of a trade-off between foraging efficiency and self-security.Therefore,it is an adaptive response to the risk of injury when hunting for larger live prey.

Modeling foraging habitats of Hume’s Pheasant (Syrmaticus humiae) in Dazhong Mountain, Yunnan, southwestern China

We modeled foraging habitats of Hume’s Pheasant (Syrmaticus humiae) on a macro-habitat level using ArcGIS in an attempt to provide scientific reference for management and restoration of habitats. Field work was conducted from March to April in 2006 and 2008, and from October to November in 2005 and 2008 in Dazhong Mountain, Yunnan Province, southwestern China. The selection of ecological factors was estimated by means of a resource selection index, distance analysis and the method of hierarchical habitat selection. The foraging habitat patches were modeled spatially by ArcGIS. The results show that actual and potential foraging patches overlapped considerably in spring and autumn. The number and total areas of patches in the autumn were smaller than those in the spring. The minimum and average areas of patches in the autumn were larger than those in the spring, while the maximum areas of actual and potential foraging patches in the autumn were equal to those in the spring. Similarity in the selection for survival and safety consideration in both seasons was the main strategy for landscape factors of habitats by Hume’s Pheasant, while seasonal difference in selecting a landscape matrix was their secondary strategy, affecting landscape factors in the habitat. Changes of foraging patches in both seasons reflect a difference of resources requirement by the bird. Fragmentation and miniaturization of foraging patches would result in the formation of a meta-population of Hume’s Pheasant.

Diet of Great Knots (Calidris tenuirostris) during spring stopover at Chongming Dongtan,China

Variable and unpredictable food resources at stopover sites bring severe challenges to migrating shorebirds. Opportunistic foraging strategies, referring to shorebirds consuming prey in proportion to their availability, allow shorebirds to replenish fuel and nutrient reserves efficiently for continuing their migration. Chongming Dongtan, located in the Yangtze River estuary of eastern China, is the first major stopover site of shorebirds on the Chinese mainland during their northward migration. We investigated the diet of Great Knots (Calidris tenuirostris) at Chongming Dongtan during the spring stopovers of 2009 and 2010 through benthos sampling and dropping analysis. The benthos samples were categorized into gastropods, bivalves, polychaetes, crustaceans and insect larvae. Dropping analysis indicated that gastropods and bivalves constituted more than 70% of the diet of the Great Knot, with Assiminea violacea and Corbicula fluminea being the most frequently consumed. Chi-square tests indicated that for each prey category, there was no significant difference between the frequency of its occurrence in the benthos samples and dropping samples during the early stopover periods of 2009 and 2010 and during the late stopover periods of 2010. Although there was a statistically significant difference between the frequency of occurrence of prey in the total macrobenthos and in the droppings of the Great Knots during the late stopover period in 2009, the more abundant prey were more frequently consumed by the Great Knots. This suggests that Great Knots adopted an opportunistic foraging strategy during their stopover at Chongming Dongtan.

In polytocous mammals,weakling neonates,but not their stronger littermates,benefit from specialized foraging

Adjusting foraging strategies is a common phenomenon within groups of animals competing for the same resource.In polytocous mammals,neonates concurrently compete for limited milk and alternate between two foraging(suckling)strategies:adaptable exploratory foraging with random sampling of teats,and ordered foraging with a tendency towards exploiting a particular suckling position.Some theoretical(game theory)models have shown that weaker siblings in particular benefit from foraging specialization(suckling order).Neonate piglets establish a well-defined suckling order that develops gradually and fluctuates throughout the lactation period,implying the existence of inter-individual differences in foraging strategies.We therefore analyzed suckling behavior in pigs to determine whether one foraging strategy was more beneficial to neonates in terms of their body weight and foraging environment.We found that intermediate and heavy littermates tended to adjust their suckling strategy according to the foraging environment;however,the selected foraging strategy did not affect their overall growth performance.Lighter individuals that consumed significantly less milk did not greatly alternate their foraging strategy according to the foraging environment but their growth rate was significantly higher whenever they performed less-exploratory foraging behavior.Although suckling order appeared to be a relatively stable behavioral phenotype,it was beneficial exclusively for weaklings.These results confirm theoretical predictions and indicate that specializing in a suckling position is a beneficial strategy for weaker,light neonates.These findings suggest that physically weaker neonates might have driven the evolution of neonatal foraging specialization.

Diet and feeding behavior of a group of high-altitude rhesus macaques: high adaptation to food shortages and seasonal fluctuations

Diet and feeding behavior data are crucial to a deep understanding of the behavioral response and adaptation of primates to a high-altitude environment.From August 2019 to June 2021,we collected data on the feeding behavior of a high-altitude rhesus macaque Macaca mulatta group from Yajiang County,Western Sichuan Plateau,which has an altitude of over 3,500 m.The results showed that feeding(33.0±1.8%)and moving(28.3±2.6%)were the dominant behavior of rhesus macaques.Macaques ate 193 food items,comprising 11 food categories from 90 species.Our study found that plant roots(30.9±30.1%)and young leaves(28.0±33.1%)were the main foods eaten by macaques.The preferred foods of rhesus macaques were young leaves,fruits,and seeds,and the consumption of these items was positively correlated with its food availability.When the availability of preferred foods was low,macaques took plant roots,barks,and fallen leaves as fallback foods.In particular,roots were a dominant food item in winter,and this way of feeding became a key survival strategy.Our results suggest that,facing the relative scarcity and strong seasonal fluctuations of food resources in high-altitude habitat,macaques adopt active foraging strategies,relying on a variety of food species and adjusting flexibly their food choices based on food availability,which may help to maximize the energy efficiency of high-altitude macaques.

Effects of environmental variability and offspring growth on the movement ecology of breeding Scopoli＇s shearwater Calonectris diomedea

Most seabird species display colonial behavior during the breeding period which implies that food resources around breeding sites can easily go depleted. Seabirds need to both reach profitable areas, which can be located far from the colony, and return to the colony regularly. In this context, flexibility in movement behavior may be crucial for breeding success. During chick-rearing, Procellariformes species can alternate short trips lasting 1-4 days for chick provisioning with longer trips for self-provisioning in what has been called a dual-foraging strategy. We analyzed foraging trips from 136 Scopoli＇s shearwaters from three Mediterranean colonies tracked with GPS during 6 chick-rearing seasons to assess whether the adoption of a dual fo- raging strategy depends on the quality of habitat surrounding the colony. We found a marked dual-foraging strategy only in birds from the Linosa colony which was the largest colony in terms of breeding pairs and was characterized by having a lower marine habitat quality. Birds from this colony performed foraging trips that extended up to 369 km from the nest and lasted more than 10 days. In general, the decision to perform long lasting trips was triggered by lower values of primary production and higher offspring weight. Contrary to expectation, the decision to feed far from the colony was not related to the parents＇ weight. At the same time, despite the higher productivity offered by distant areas, the higher proportion of long trips performed by birds breeding in poor areas was not sufficient to maintain the same body mass as the ones breeding in richer areas [Current Zoology 60 （5）： 622-630, 2014].

Diet of Chinese skink, Eumeces chinensis: is prey size important?

The diet of the skink,Eumeces chinensis(Lacertilia:Scincidae),in Xiamen(Amoy),China was examined using stomach analysis during April and May,and its selection of prey size was tested by feeding trials.Insects(primarily Coleoptera,Lepidoptera,and Orthoptera),gastropods and arachnids constituted most of the E.chinensis diet,but earthworms,leeches,crustaceans and fish were also consumed.In the field,male skinks ate more prey items that were 11–20 mm in length than other size classes.When presented with a choice of different-sized prey in the laboratory,male E.chinensis exhibited a strong preference for prey items 11–20 mm in length over other size classes.The relationship between prey size and handling time was exponential,indicating that there is an upper limit to the ability of E.chinensis to process prey.Mean energy intake for handling different-sized prey showed that selection of midsize-class prey items would provide male E.chinensis with the most energy-efficient prey option.These results indicate that prey size selection in E.chinensis favors maximization of rates of energy intake,which is in agreement with optimal foraging theory.