acta ethologica最新文献

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.

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.

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.

The activity of small invasive mammals, the American mink (Neovison vison) and the coypu (Myocastor coypus), was monitored in western part of Slovakia. Camera traps were located at 9 localities where these animals occur and were monitored throughout all four seasons. The activity of these two invasive species was analysed with regard to the habitat type and environment and, but especially, to the relationship to season, daily period, part of the day and activities. The following animal activities were observed: environmetal exploration, movement, swimming, stationary, grooming, play, flee, feeding, change of environment, mating behaviour and territorial marking. In case of the coypu, crepuscular and nocturnal activities were prevalent. Activity during daytime occurred mostly during winter days with low temperatures. On the other hand, American minks were mostly diurnal. The shift in behaviour compared to American minks in their native environment could be a sign of its adaptation to a new environment. Our research also showed seasonal changes in activity of both invasive mammals. This research could serve as a basis for management schemes to combat the presence and dispersal of these two invasive mammal species.

The Brazilian ruby, Heliodoxa rubricauda, is a forest species of hummingbird endemic to the Atlantic Forest. It belongs to an Andean clade of birds with robust and strong legs and adapted to feed on inflorescences of plants from high regions and influenced by strong winds. It occurs from northeastern to southern Brazil on slopes, sierras, and mountains and has the little-known behavior of bathing in waterfalls and forest streams. Based on five field observations made in the state of São Paulo, and records available from online photo platforms, we concluded that H. rubricauda is the only species of hummingbird in Brazil that bathes by settling on rocks of forest waterfalls with medium to strong currents. This behavior is made possible by the robust and strong legs the species inherited from its evolutionary lineage, which, in the Atlantic Forest, are used for feeding, defense, and bathing. We hypothesize that this behavior is more efficient for body hygiene than other existing behaviors because it allows a greater amount of water to pass over the body, thereby eliminating traces of food and parasites, in addition to reducing risks of predation.

Crab-eating mongooses (Herpestes urva) are widely distributed across Southeast Asia. In Taiwan, the mongoose (H. urva formosanus, endemic subspecies) is a protected species under the Wildlife Protection Act. Crab-eating mongooses have been observed near streams, riversides, agricultural lands, and shallow mountain areas. Additionally, as described in this short communication, by using a remote camera, we observed a small population of mongooses in the coastal forest in Kenting National Park in Taiwan. The mongooses in the coastal forest were observed eating land hermit crabs, which is the first-ever recorded observation of this behavior. Mongooses are known to consume crabs (Brachyura), insects, and some small reptiles. However, this article presents the first record case of mongooses using stone anvil to crack open land hermit crabs. From our observations and field records, we determined that mongooses use flat rocks as anvils and their front paws to tap hermit crabs’ shells repeatedly to break the shells and remove the hermit crabs. We also observed that the mongooses only ate the abdomens of large hermit crabs. Additional studies are necessary to determine why the mongooses migrated to the coastal forest and how they learned to open hermit crab shells. This behavior of mongooses might help them move into living in coastal forests.

Predation strategies are often habitat-dependent; therefore, contrasting biomes, such as rainforests and seasonally dry forests, may be useful for understanding how the environment influences predatory behavior. The aim of this study was to evaluate the prey capture behavior of scorpions from contrasting habitats in northeastern Brazil. The scorpions’ use of the stinger and movement probability after prey capture were analyzed. We collected 120 scorpions, 60 from the Atlantic Forest and 60 from the Caatinga drylands. Our results indicate that scorpions from the Atlantic Forest tended to use their stinger more frequently than those from the Caatinga habitat. We also found that Caatinga scorpions moved approximately 40% more after prey capture than the Atlantic Forest species. Environmental pressures related to the metabolic costs of venom production and potential predation risk may partially explain the differential behavior observed in this study. Therefore, our results suggest that despite the morphological differences between species, animals from contrasting habitats may show different prey capture strategies.

Heterospecifics eavesdrop on mobbing calls and respond with appropriate behavior, but the functional aspects are less studied. Here, I studied whether jays (Garrulus glandarius) eavesdrop on blackbird (Turdus merula) mobbing calls in comparison to blackbird song. Furthermore, it was studied whether jays provided with extra information about predators differ in their response. Three different experimental designs were carried out: (1) control playback of blackbird song to control for the species’ presence, (2) experimental playback of different mobbing events of blackbirds towards different predators, (3) experimental playback similar to (2) but combined with different predator models. In the combined experiments, mobbing calls were tied to the respective visual stimuli. Comparing the experiments with and without predator presentation, a similar number of jays occurred during the playback-only experiment (n = 7) and the playback combined with model presentation (n = 6). However, during the playback-only experiment, jays approached the speaker closer and stayed for longer time in the nearer surrounding. These results show that jays need extra information to make an informed decision.