Fruit scent as an indicator of ripeness status in ‘bat fruits’ to attract ‘fruit bats’: chemical basis of chiropterochory

Abstract

In the tropics, animal-mediated seed dispersal is the most frequently occurring dispersal syndrome, which includes traits that aid in attracting both diurnal and nocturnal dispersers. However, some plants bear fruits with special traits that make them less conspicuous to diurnal frugivores to make them exclusively available to nocturnal frugivores such as bats, which are called ‘bat fruits’. Since these fruits remain drab green in colour throughout their phases of ontogeny, the difference in scent compounds is predicted to help bats to assess their ripeness status. In this study, we specifically examined the behavioural repertoires associated with fruit removal such as ‘search latency’ and ‘number of attempts’ taken by two small-sized fruit bats (Cynopterus sphinx and Rousettus leschenaulti) that feed ex situ and a large-sized fruit bat (Pteropus giganteus) that feed in situ on a bat fruit (Madhuca indica). No fruit was removed on the ‘first’ attempt itself by both the bats; instead, they made multiple (two to six) repeated search attempts to the same bunch of fruits, which is presumably a behavioural mechanism underlying assessing the ripeness status to increase the chance of removal of ripe fruits. The emission of scent compounds was examined using a high-sensitivity headspace proton-transfer-reaction mass spectrometer in real time without any pre-treatment. As predicted, the fruits at the predispersal (unripe) and dispersal (ripe) phases differed significantly from each other in terms of concentration (intensity) of volatile compounds although no difference was inferred in terms of their composition. This study, thereby, highlights the underlying chemical basis of the foraging behaviour of fruit bats while foraging on bat fruits that finally effectuate its seed dispersal (chiropterochory).

Interaction between vasotocin and gonadal hormones in the regulation of reproductive behavior in a cichlid fish

Abstract

Vasotocin (VT) has been associated with the regulation of different aspects of social behavior (e.g., mating and aggression). Given the fact that androgens are also known to regulate reproductive behavior, we hypothesized that VT and androgens could be interacting, rather than acting independently, in the regulation of reproductive behavior. In the present study, we aimed to understand the effect of VT and its interaction with gonadal hormones (putatively androgens) on different aspects of reproductive behavior of a polygynous and territorial cichlid fish, the Mozambique tilapia (Oreochromis mossambicus). Using a within-subject design, we treated territorial males, that were previously castrated or sham-operated, with different dosages of VT as well as with a V1A receptor antagonist (Manning compound) and subsequently analyzed their behavior towards females and towards an intruder male. Our results showed that VT affected the behavior of territorial males towards females but not towards males. Specifically, VT-treated males interacted less with females (i.e., spent less time touching the transparent partition that allowed visual contact with females) and were less aggressive towards females than saline-treated males. Moreover, in sham-operated males, blocking V1A receptors increased the frequency of bites towards females in comparison to saline-treated males, but not in castrated males. This result suggests that VT down-regulates aggressiveness towards females through the action of V1A receptors in the gonads (putatively decreasing androgen secretion), and that androgens up-regulate this behavior. In summary, our results suggest that VT may modulate social behavior, through an interaction with gonadal hormones.

Cannibalism in common kestrel (Falco tinnunculus)

Abstract

We report two separate observations of adult male common kestrel (Falco tinnunculus) killing and feeding upon second-year (SY) conspecifics in Israel. On 22 January 2022, while touring the Givat Et Nature Reserve, we observed an SY kestrel locked in aerial combat with an adult. They landed with the SY on his back, who was killed by decapitation by the adult, who continued to feed on the breast muscle. Earlier, on 24 January 2013, in the area of the Latrun Junction, two males were seen in flight with their talons locked together and screeching at each other. Eventually, they crash-landed with the adult on the top and pecking at the SY conspecific. They remained in this position for more than 30 min with the adult plucking the breast feathers of the SY who struggled incessantly but was unable to escape the hold of the adult and eventually succumbed to the injuries. The adult subsequently fed from the breast muscle of the SY. Although avian cannibalism is known in several Falco spp., this is the first reported for the common kestrel.

Use of crowdsourced images for determining 2D:4D and relationship to pro-environmental variables

Abstract

The primary purpose of this study was to examine whether 2D:4D ratios (a putative measure of prenatal androgen exposure) could be determined using participant-submitted hand images. The secondary purpose was to examine whether 2D:4D ratio was associated with pro-environmental behaviors, attitudes, and empathy, given the recent literature linking sex to environmental attitudes and actions. Participants (N = 1065) were asked via an online survey to submit a clear photograph of their right hand, palm side up. Participants also completed a questionnaire to assess (a) demographics, (b) dispositional empathy, and (c) environmental attitudes and behavior. A 2D:4D ratio was calculated for each participant, and the quality of each image was classified as poor, moderate, or good. We then examined the reliability of the 2D:4D image measurements, and the relationship between 2D:4D and our environmental measures. 2D:4D ratios fell somewhat outside of previously reported ranges, but the measurements did show acceptable intra-rater consistency. Although we did not find a sex difference in 2D:4D, we did find a sex by ratio interaction for both empathy and the number of pro-environmental behaviors in which individuals had engaged. Specifically, as 2D:4D ratio increased, males reported lower empathy and less engagement in pro-environmental behaviors, whereas females reported more engagement in pro-environmental behaviors (but no differences in empathy). These findings were contrary to expectations, as we anticipated that greater digit ratios (i.e., feminized) would be associated with greater empathy and pro-environmental behaviors. Overall, the findings of this study present a preliminary examination of the utility of measuring digit ratio with online samples. Furthermore, our results provide information regarding the complex relationship between sex and pro-environmental behaviors.

Coexistence with an invasive species in the context of global warming lead to behavioural changes via both hereditary and ontogenetic adjustments to minimise conflict

Abstract

Global warming and invasive species often act synergistically to threat native communities. The Neotropical Poeciliidae have extensively been introduced to control populations of malaria-transmitting mosquitoes and are now successful invaders around the world. Poecilids introduced to a habitat in the fringe of its thermal tolerance will be increasingly more competitive as temperature increases. This can lead to either local extinction or rapid adaptation of native species. We evaluated if the introduction of two-spot livebearers (Pseudoxiphophorus bimaculatus) has led, after approximately 28 years, to hereditary differences between amarillo fish (Girardinichthys multiradiatus) from an invaded and a non-invaded adjacent temperate mountain lake. Laboratory-born F1 amarillo from the two lakes were raised in either presence or absence of feeding competition with two-spot livebearers. F1 females from Zempoala foraged for shorter periods and were more frequently aggressive than those from Tonatiahua, whereas Zempoala males were quicker to start foraging, did so for shorter periods, and were less likely to fight with their own, than males from Tonatiahua. Similarly, amongst fish from Zempoala reared in the presence of competition with P. bimaculatus, females were slower to start foraging and foraged for shorter periods, and males had reduced foraging and agonistic behaviour, than those reared facing only conspecific competition. We conclude that temperature-dependent behavioural differences have arisen between populations of a native fish, seemingly linked to foraging in a competitive environment and the tendency to be aggressive towards conspecific and heterospecific fish. These differences are the result of both local adaptation and behavioural flexibility.

Poison frog social behaviour under global change: potential impacts and future challenges

Abstract

The current and cascading effects of global change challenges the interactions both between animal individuals (i.e. social and sexual behaviour) and the environment they inhabit. Amphibians are an ecologically diverse class with a wide range of social and sexual behaviours, making them a compelling model to understand the potential adaptations of animals faced with the effects of human-induced rapid environmental changes (HIREC). Poison frogs (Dendrobatoidea) are a particularly interesting system, as they display diverse social behaviours that are shaped by conspecific and environmental interactions, thus offering a tractable system to investigate how closely related species may respond to the impacts of HIREC. Here, we discuss the potential impacts of global change on poison frog behaviour, and the future challenges this group may face in response to such change. We pay special attention to parental care and territoriality, which are emblematic of this clade, and consider how different species may flexibly respond and adapt to increasingly frequent and diverse anthropogenic stress. More specifically, we hypothesise that some parents may increase care (i.e. clutch attendance and distance travelled for tadpole transport) in HIREC scenarios and that species with more generalist oviposition and tadpole deposition behaviours may fare more positively than their less flexible counterparts; we predict that the latter may either face increased competition for resources limited by HIREC or will be forced to adapt and expand their natural preferences. Likewise, we hypothesise that human-driven habitat alteration will disrupt the acoustic and visual communication systems due to increased noise pollution and/or changes in the surrounding light environment. We highlight the need for more empirical research combining behavioural ecology and conservation to better predict species’ vulnerability to global change and efficiently focus conservation efforts.

Promiscuity in the Greater Rhea: a genetic approach

Abstract

Greater Rheas (Rhea americana) have a social mating system in which several females lay eggs in communal nests, and males incubate and care for chicks. Behavioural observation methods used so far are insufficient to unravel if females form a cohesive “harem,” simultaneous polyandry (promiscuity) occurs in the wild, and multipaternity occurs in each clutch. We used molecular markers to conduct for the first time a genotype-based sibship and parentage assignment analysis among reproductive individuals and their offspring, within and between nests, in a wild Greater Rhea population of central Argentina. In a 4800-ha area, we found five nests from which we collected complete clutches and feathers of incubating males. We successfully determined the genotypes of three males and all 141 offspring at 8 microsatellite loci. We inferred the parents involved in matings and their genotypes based on offspring’s genotypes. A total of 37 males and 47 females were engaged in the assigned pairings, and one incubating male did not fertilise any egg. We obtained three main novel results that enlighten the mating system of Rheas: (a) females do not form “harems”; (b) there is evidence of promiscuity; and (c) incubator male does not father the majority of offspring from his nest. The strategy of Greater Rheas is to copulate with several individuals simultaneously and lay eggs in different nests, independently of whether or not the incubating male fathers those eggs. These results provide a new and significant step in understanding the complex mating system of this ratite.

First evidence for active carnivorous predation in the European ground squirrel

Abstract

The Sciuridae family is generally referred to as herbivorous and occasionally omnivorous. Although sciurids are known to opportunistically feed on carcasses of other vertebrates (including cannibalism), the active predation on vertebrates is presumably rare. Here, we present a case of a European ground squirrel (Spermophilus citellus) catching and eating a young Eurasian tree sparrow (Passer montanus) accompanied by photographic evidence. This is the first documented observation of bird-killing behavior in this endangered rodent. The incident happened at the end of spring (beginning of June) when the plant proteins are still scarce. At this time of the season, the ground squirrels are exhausted by reproduction efforts and need highly energetic food in order to recover.

Occurrence of long-finned pilot whales (Globicephala melas) and killer whales (Orcinus orca) in Icelandic coastal waters and their interspecific interactions

Abstract

Long-finned pilot whales and killer whales are widely distributed across the North Atlantic, but few studies have reported their occurrence in Icelandic coastal waters. Here, we use sightings data from research platforms and whale watching tours in six regions of Iceland from 2007 to 2020 to show that the occurrence of long-finned pilot and killer whales varied with region and season. Killer whales were regularly encountered in the south of Iceland during summer and west of Iceland during winter/spring. Long-finned pilot whales were only seen during the summer and were most often encountered in the south, west, and northwest of Iceland. Long-finned pilot whale occurrence in the south of Iceland appeared to increase during the study period but killer whale occurrence showed no noticeable changes. Long-finned pilot whales were sighted often in the areas that were also frequented by killer whales and interspecific interactions were commonly observed when both species co-occurred. Interactions appeared to be antagonistic, with killer whales often avoiding long-finned pilot whales and sometimes fleeing at high speed, similar to what has been described elsewhere in the North Atlantic. In the majority of interactions observed (68%), killer whales avoided long-finned pilot whales by moving away, but in 28% avoidance was at high speed with both species porpoising. This variability in the type of behavioural responses indicates that interactions may be more complex than previously described. We discuss regional trends in long-finned pilot whale and killer whale sightings and potential drivers of the observed interactions.