Agonistic and mating behaviour of the endemic lizard Trachylepis atlantica from the Fernando de Noronha archipelago, Brazil

The skink Trachylepis atlantica is endemic to the Fernando de Noronha archipelago. Although this species is abundant in the archipelago, it is increasingly threatened by invasive species, predation, and anthropic interference. However, little is known about its natural history. Here we report on territory use, male-male combat, and mating behaviour of freeranging T. atlantica. During the dry season, we observed two bouts of male combat and two copulations, which suggests some mating seasonality. In male combat, T. atlantica displays ritualised agonistic behaviour with escalated aggressiveness that include - i) visualisation, approaching or following, ii) visual display, iii) bite and body confrontation, and iv) dominance. Adult males were always alert to invaders within their territories. After combat, resident males showed scars on their heads resulting from agonistic encounters. During the two copulations, we observed courtship, immobilisation, and mating.

Sex differences in behavioural and anatomical estimates of visual acuity in the green swordtail Xiphophorus helleri

Among fishes in the family Poeciliidae, signals such as colour patterns, ornaments, and courtship displays play important roles in mate choice and male-male competition. Despite this, visual capabilities in Poeciliids are understudied, in particular visual acuity, the ability to resolve detail. We used three methods to quantify visual acuity in male and female green swordtails (Xiphophorus helleri), a species in which body size and the length of the male's extended caudal fin (‘sword’) serve as assessment signals during mate choice and agonistic encounters. Topographic distribution of retinal ganglion cells (RGC) was similar in all individuals and characterized by areas of high cell densities located centro-temporally and nasally, as well as a weak horizontal streak. Based on the peak density of RGC in the centro-temporal area, anatomical acuity was estimated to be approximately 3 cycles/degree (cpd) in both sexes. However, a behavioural optomotor assay found significantly lower mean acuity in males (0.8 cpd) than females (3.0 cpd), which was not explained by differences in eye size between males and females. An additional behavioural assay, in which we trained individuals to discriminate striped gratings from grey stimuli of the same mean luminance, also showed lower acuity in males (1-2 cpd) than females (2-3 cpd). Thus, although retinal anatomy predicts identical acuity in males and females, two behavioural assays found higher acuity in females than males, a sexual dimorphism which is rare outside of invertebrates. Overall, our results have implications for understanding how Poeciliids perceive visual signals during mate choice and agonistic encounters.

Sex recognition and agonistic strategies of male and female crayfish

Intraspecific communication is essential for agonistic and mating behaviours. Agonistic strategy of males must change according to the sex of opponents and that of females is also dependent on their physiological state as to whether they are brooding or not. We have analysed here the agonistic encounters between pairs of male and female crayfish in various combinations to reveal the interaction between agonistic and mating behaviours. After male crayfish became dominant, they aggressively chased subordinate males with attacks, while they did not attack female opponents. Furthermore, the agonistic behaviour of males changed depending on whether females were ovigerous or not. On the other hand, two females showed intense combats despite being ovigerous or not. Crayfish discriminated the sex of opponents via chemical signals in the urine. However, the dominant and subordinate social order of crayfish had no effect on selecting mating partners.

Hummingbird (Aves: Trochilidae) assemblage using resources from the exotic African tuliptree, Spathodea campanulata (Bignoniaceae) in a Neotropical altered environment, southeastern Brazil

The non-native African tuliptree, Spathodea campanulata (P. Beauv), is widely distributed in altered Neotropical environments, where hummingbirds are important pollinators. We investigated the assemblage of hummingbirds which fed on its nectar and described their behavior, to understand possible influences of the exotic tree on the territorial behavior in an altered environment in southeastern Brazil. Seven species fed on flower resources, mainly Eupetomena macroura (Gmelin, 1788), Amazilia lactea (Lesson, 1832), and Florisuga fusca (Vieillot, 1817). Visiting time was positive correlated with number of flowers accessed, but in most visits, hummingbirds get the nectar by pillage, instead of frontal access. Flower availability varied throughout months; however, we found no evidence of significative correlation between available flowers and number of agonistic encounters. Despite a high number of animal-plant interactions and a strong territorialism of some species observed in African tuliptree foraging site, there may be other plants at local scale influencing the behavioral patterns observed.

Beyond a feeding and thermoregulatory structure: toucan’s bill as a sword and pincer

Toucans (Ramphastidae) have always attracted researcher’s attention for their exuberant bill shape and size, which function has been often related to feeding strategies and thermal regulation. In this study, we discuss the importance and use of the bill by Ramphastidae species in intraspecific disputes. We present novel data and video recordings on agonistic encounters between females of the Spot-billed Toucan Selenidera maculirostris, along with a compilation of data from the Brazilian citizen science platform WikiAves and previous studies on six other Ramphastidae species. Until now, only a couple of species was known for using their bill in fights against conspecifics. Our study highlights the between-species behavioral similarities and the widespread occurrence of such behavior in the family, suggesting that this may be more common than previously thought and proposing hypotheses on the likely roles of such intraspecific contests.