Commentary on emotion in sharks

While studying the behaviour of a community of blackfin reef sharks, there was a four month long episode during which the entire company of residents and their visitors showed evidence of feeling a negative emotion towards me. They directed a variety of menacing gestures towards me, and their behaviour escalated until they began battering my kayak on my arrival in their range. Underwater, three would have slammed me personally had I not fought them off. Their behaviour suggested that their cognitive functions are complex, for they held their negative attitude in mind long-term. Two years later, under different conditions, they conveyed, via body language, a positive emotion. Social learning, social buffering, and emotional contagion were also displayed in their actions.

Multiple cues guarantee successful predation by a Neotropical wasp

Predatory social wasps are well studied in several aspects; however, foraging behaviour, especially that which takes place away from the nest at often unpredictable locations, or specialized behaviours to find and subdue prey are not well understood. In the Brazilian tropical savanna, the Polistinae wasp Brachygastra lecheguana is specialized in preying on some endophytic weevil larvae which develops inside floral buds. We hypothesized that these wasps utilize a combination of different mechanisms such as visual, chemical (odour) and possible tactile cues to find the weevil larvae. Using a combination of experimental manipulations (visual; chemical; visual/chemical) we tested the wasp’s ability to detect the endophytic larvae in the field. Additionally, we checked the ability of this wasp to detect vibrations produced by the weevils inside the buds. Our results suggest that the B. lecheguana wasp utilizes a sequence of eco-physiological mechanisms to find the endophytic larva inside floral buds: sight, smell, and perhaps touch. The use of multiple cues by this wasp guarantees such a high rate of predation on endophytic beetles that the wasp may have positive implications (reduction in weevils’ infestation) for the future of the host plant’s reproduction.

Gregariousness and intraspecific aggression in Iberian bullfinches (Pyrrhula pyrrhula iberiae) throughout the year

This study provides novel information about gregariousness and intraspecific aggression in Iberian bullfinches (Pyrrhula pyrrhula iberiae) in northwestern Spain. Small monospecific parties never exceeding 10 individuals were seen throughout the year, larger in winter on average. Males considerably outnumbered females within the groups. Adult flocks were frequent only in winter. In spring, many of the adult groups were mixed-sex assemblages composed of pairs plus supernumerary males. Sightings of juvenile groups, up to seven individuals, were common in summer–autumn. The vigilance role in mixed-sex assemblages, including pairs, appeared to be the responsibility of males based on sex-specific vigilance rates. The highest frequency of aggressive encounters, mainly male against male, occurred during the breeding season, associated with mate defence. Females attacked males, not the contrary, which supports reversed sexual dominance in bullfinches. Gregariousness probably acted as an anti-predatory and foraging strategy.

Inter-individual differences of calling and exploratory behaviour in a lebinthine cricket species hint at different mate-finding strategies

Individual fitness can be boosted by behavioural strategies that maximise mate-finding probability while minimising predation risk. Animals that use acoustics to find mates may benefit from using both stationary calling and active exploration, but these also expose them to different types of predators. Studying calling and searching behaviours concurrently allows us to understand their evolutionary trade-offs between survival and reproduction. Unlike most other crickets, lebinthine males alternate between singing and exploration to find females, which offer a unique and excellent opportunity to test for inter-individual differences and behavioural syndrome between call properties and exploratory behaviours. Our data demonstrate that call properties and exploratory behaviour were repeatable. We did not, however, find that call properties correlate with exploration as some consistently exploratory individuals produce longer calls while others produce shorter calls. Our study suggests that lebinthine males use different combinations of calling and exploratory behaviours to cope with unpredictable risk–benefit scenarios.

Who cares for the eggs? Analysis of egg attendance behaviour in Ranitomeya imitator, a poison frog with biparental care

Dendrobatid poison frogs are known for their diverse parental care behaviours, including terrestrial egg attendance. While usually this behaviour is conducted by males, this study compared the pre-hatching investment of males and females in Ranitomeya imitator, a species with biparental care. Although males tended to spend more time with their eggs overall, there was no difference between sexes when comparing different types of care behaviour. Furthermore, both sexes increased general care behaviour when caring for more than one clutch. The finding that the sexes are relatively equal in their contribution to basic parental care forms provides a basis to understand why biparental care is stable in this species.

The squeaking vocalization of grey wolves (Canis lupus): individuality in a close-range affiliative mammalian vocalisation

Wolves (Canis lupus) frequently use the close-range squeaking vocalization, a soft, multi-unit, high-pitched tonal vocalisation. We examined the social and movement contexts of the occurrence and acoustic characteristics of squeaking from videotapes of pack-reared, pack-living captive wolves living in semi-natural conditions at the Canadian Centre for Wolf Research over a three-year period. We only examined squeaking vocalisations for which the sender and potential receiver(s) could be determined. Wolves squeaked in many contexts, especially when approaching other wolves in prosocial and food contexts. Some wolves squeaked more than others. Acoustically, squeaking vocalisations were individually identifiable, primarily through frequency characteristics. Contextual use suggests that squeaking conveys the friendly motivation of an approaching wolf and in aggressive situations, a motivation to defuse or decrease aggression. This close-range vocalisation may play an important role in controlling and coordinating social interactions within the pack.

Tools and food on heat lamps: pyrocognitive sparks in New Caledonian crows?

Fire has substantially altered the course of human evolution. Cooking kindled brain expansion through improved energy and time budgets. However, little is known about the origins of fire use and its cognitive underpinnings (pyrocognition). Debates on how hominins innovated cooking focus on archaeological findings, but should also be informed by the response of animals towards heat sources. Here, we report six observations on two captive New Caledonian crows (Corvus moneduloides) contacting heat lamps with tools or placing raw food on them. The tools became singed or melted and the food had browned (and was removed). These results suggest that New Caledonian crows can use tools to investigate hot objects, which extends earlier findings that they use tools to examine potential hazards (pericular tool use), and place food on a heat source as play or exploration. Further research on animals will provide novel insights into the pyrocognitive origins of early humans.

Space use and parental care behaviour in Andinobates claudiae (Dendrobatidae)

The selection of habitats with potential reproductive resources may maximize individual reproductive success and overall fitness. Dendrobatid frogs display remarkable parental care which is associated with water bodies (phytotelmata) contained in plants with characteristics that are important to offspring survival. It has been shown that the size of phytotelmata is a key factor that drove the divergence in parental care patterns in poison frogs and that the distribution of reproductive resources can influence space use in these species. Here, we investigated parental care strategies and the influence of reproductive resource distribution on space use patterns in a wild population of Andinobates claudiae in Bocas del Toro, Panama. We identified the phytotelmata characteristics that predict tadpole deposition and analysed the association between the spatial distribution of phytotelmata and spatial use of males and females. Our observations showed that this species mates polygamously and exhibits male parental care. We found that male frogs have smaller kernel density home ranges and core areas compared to females, and that space use is related to the density of Heliconia plants whose axil cavities are used for tadpole rearing. Furthermore, we found that tadpoles were more frequently found in phytotelmata that were at lower heights and contained larger water volumes. Fathers invested time inspecting multiple cavities and travelled further than predicted from their territories to find suitable deposition sites. Our observations suggest a selective choice of phytotelmata regarding tadpole deposition, where distribution and quality of cavities might influence parental care decisions.