Consistency and flexibility in solving spatial tasks: different horses show different cognitive styles

Individual animals vary in their behaviour and reactions to novel situations. These differences may extend to differences in cognition among individuals. We tested twenty-six horses for their ability to detour around symmetric and asymmetric obstacles. All of the animals were able to get around the barrier to reach a food target, but varied in their approach. Some horses moved slowly but were more accurate in choosing the shortest way. Other horses acted quickly, consistently detoured in the same direction, and did not reliably choose the shortest way. The remaining horses shifted from a faster, directionally consistent response with the symmetric barrier, to a slower but more accurate response with the asymmetric barrier. The asymmetric barrier induced a reduction in heart rate variability, suggesting that this is a more demanding task. The different approaches used to solve the asymmetric task may reflect distinct cognitive styles in horses, which vary among individuals, and could be linked to different personality traits. Understanding equine behaviour and cognition can inform horse welfare and management

Sequestration of defenses against predators drives specialized host plant associations in preadapted milkweed bugs (Heteroptera: Lygaeinae)

AbstractHost plant specialization across herbivorous insects varies dramatically, but while the molecular mechanisms of host plant adaptations are increasingly known, we often lack a comprehensive understanding of the selective forces that favor specialization. The milkweed bugs (Heteroptera: Lygaeinae) are ancestrally associated with plants of the Apocynaceae from which they commonly sequester cardiac glycosides for defense, facilitated by resistant NaNa+/K+-ATPases and adaptations for transport, storage, and discharge of toxins. Here, we show that three Lygaeinae species independently colonized four novel nonapocynaceous hosts that convergently produce cardiac glycosides. A fourth species shifted to a new source of toxins by tolerating and sequestering alkaloids from meadow saffron (Colchicum autumnale, Colchicaceae). Across three milkweed bug species tested, feeding on seeds containing toxins did not improve growth or speed of development and even impaired growth and development in two species, but sequestration mediated protection of milkweed bugs against two natural predators: lacewing larvae and passerine birds. We conclude that physiological preadaptations and convergent phytochemistry facilitated novel specialized host associations. Since toxic seeds did not improve growth but either impaired growth or, at most, had neutral effects, selection by predators on sequestration of defenses, rather than the exploitation of additional profitable dietary resources, can lead to obligatory specialized host associations in otherwise generalist insects

Differential Bird Responses to Colour Morphs of an Aposematic Leaf Beetle may Affect Variation in Morph Frequencies in Polymorphic Prey Populations

The selection of prey by predators should, theoretically, favour uniformity in the warning signals displayed by unpalatable prey. Nevertheless, some aposematically coloured species are polymorphic. We tested the hypothesis that colour morphs of unpalatable prey differ in the efficacy of their aposematic signal for birds, thereby affecting the selective advantages of these morphs. We used colour morphs (red-and-black light, red-and-black dark and metallic) of the chemically defended leaf beetle Chrysomela lapponica. In laboratory experiments, naïve great tits (Parus major) attacked live beetles of all colour morphs at the same rate. By contrast, wild-caught tits attacked light beetles at first encounter at the same rate as a novel control prey, but significantly avoided both dark and metallic beetles. Beetles of all colour morphs were similarly unpalatable for birds, and about half of the attacked beetles were released unharmed. Avoidance learning was similarly fast for all three leaf beetle morphs. However, in the next-day memory test, the dark beetles were attacked at a greater rate than beetles of two other morphs, indicating their lower memorability. A field experiment suggests that at low C. lapponica population densities, dark beetles have a survival advantage over light beetles, potentially due to the lesser conspicuousness of the dark pattern; however, when the density is high, dark beetles lose this advantage due to the low memorability of their pattern. Thus, the direction of selective bird predation on prey colour morphs may depend on prey density and thereby contribute to temporal shifts in colour morph frequencies following population fluctuations.</p

The evolution and ecology of multiple antipredator defences

Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies.</p

Global selection on insect antipredator coloration

Natural selection has repeatedly led to the evolution of two alternative antipredator color strategies—camouflage to avoid detection and aposematism to advertise unprofitability—but we lack understanding of how ecological context favors one strategy over the other. We conducted a globally replicated predation experiment at 21 sites on six continents to test how predator community, prey community, and visual environment influenced the predation risk of 15,018 artificial paper “moth” prey with cryptic or warning coloration. Results indicated that aposematic strategies fare better in environments with low predation intensity, whereas camouflage strategies are advantaged when other camouflaged prey species are rare and when light levels are low. This study demonstrates how multiple mechanisms shape antipredator strategies, helping to explain the evolution and global distribution of camouflaged and aposematic animals

Territory size and habitat selection in subadult and adult males of Black Redstart (Phoenicurus ochruros) in an urban environment

Territory size, distribution of territories and habitat selection were studied in Black Redstart (Phoenicurus ochruros) populations in three urban habitats (garden city, old and new housing estates) of Prague (Czech Republic). We tested if the territory size and quality of territories occupied by adult and subadult males differed from each other. Average territory size of the adult males was 1.21 ± 0.80(SD) ha and of the subadult males 1.08 ± 0.58(SD) ha. This difference was not statistically significant. Moreover, males of particular age-class were not spatially clustered. Microhabitat analysis shows that the habitat selection depends on the presence of buildings. Apparently buildings offer a good nesting, singing and foraging places for the Black Redstart. The territory size of Black Redstarts differed between habitats, being largest in the garden city (1.98 ± 1.06 (SD) ha), intermediate in the old housing estate (1.48 ± 0.45 (SD ha) and smallest in the new housing estate (0.85 ± 0.33 (SD) ha). Our results indicate that in urban environment the relationships between adult and subadult territory owners differ from those referred to in mountain villages

Nestling diet of the Common Magpie (Pica pica) in urban and agricultural habitats

Several processes may be responsible for the urbanization of the Common Magpie (Pica pica), a species spreading widely in European towns during the last 50 years. Greater supply or better availability of food could play a role in the successful colonization of urban habitats by this species. We compared the nestling diet of Magpies within (urban) and adjacent to the city (rural) of Prague, Czech Republic, using the neck-collar method, and studied parental foraging behavior and micro-habitat associations in the city of Prague. Although the nestling diet was different between urban and rural areas, invertebrates (mainly Coleoptera) were the most frequent prey in both areas. Anthropogenic food was more abundant in urban than in rural areas. The nestling diet differed from the potentially available food supply in both urban and rural areas: Annelida and Lepidoptera were preferred, while Isopoda, Diplopoda, Orthoptera and Hymenoptera were neglected. In urban areas, Magpies foraged actively (i.e., by walking) and by perching. Prey was collected mostly from the ground. Magpies foraged mainly at sites covered with short vegetation. Utilization of short vegetation was proportional to its availability, whereas tall vegetation was used less than could be expected by availability. Short vegetation dominated the home ranges of Magpies in urban areas, while tall vegetation was more common in the Magpie home ranges in rural areas