acta ethologica最新文献

Water turbidity deteriorates visibility and thereby may change the physiology and behavior of aquatic animals that rely on vision. In the guppy fish (Poecilia reticulata), a key element in the mating behavior and reproductive success of males is female mate choice, which is predominantly based on visual signals. Females choose attractive males based on body coloration, and males court females by displaying their coloration. Here, we demonstrate that guppy males exhibit morphological and behavioral adjustments in response to changes in the visual environment. Males reared in turbid water had more conspicuous coloration than males reared in clear water, with higher intensity of carotenoid-based and ultraviolet colors, but not a larger area of red spots on the body. However, they performed less courtship displays in turbid water than males reared in clear water performed in clear water. Thus, increased coloration in turbid-water males was not accompanied by increased effort to display it. Although our findings demonstrated developmental plasticity in mating-related traits, turbidity-induced alteration in coloration did not match behavior change as could be predicted by favoring male attractiveness.

Animals have evolved a variety of mechanisms to detect and avoid predation. The non-vocal sounds produced by some bird species during takeoff flights have been considered to function as an alarm call, because they may convey information about predation risk. Here, we experimentally investigated the effects of the non-vocal sound (wing trills) produced by the scaled dove (Columbina squammata) on antipredation behaviours of conspecifics. We evaluated the individual response to playbacks of the wing trill stimulus and compared it to the response to other two control stimuli (vocalizations of the scaled dove and the southern house wren). We found that doves’ probability to become vigilant or to display freezing behaviour was higher after a wing trills stimulus in comparison to the other playback stimuli. These results suggest that wing trill production in scaled doves communicate potential risks and are considered by the individuals in the decision-making process, but we cannot rule out the possibility that any takeoff flight sound might also promote antipredator responses.

Animals can form groups for various reasons including safety from predators, access to potential mates and benefits of allo-parental care. However, there are costs associated with living in a group such as competition for food and/or mates with other members of the group, higher chances of disease transmission, etc. Group size dynamics can change with the biotic and abiotic environment around individuals. In the current study, we explored the links between group size dynamics and intestinal parasites of Indian peafowl (Pavo cristatus) in the context of seasons and food provisioning. Data for group size was collected across three seasons (pre-monsoon, monsoon and post-monsoon) at three field sites (Morachi Chincholi, Nashik and Rajasthan). Individual and group sightings of peafowl were noted down along with group size and composition (no. of males, females, adults, juveniles and sub-adults). Faecal samples were collected from food provision and non-provision areas across the same three seasons at same field sites. Parasite load in the samples was quantified using microscopic examination. Group size was significantly higher in pre-monsoon season as compared with monsoon and post-monsoon seasons. Monsoon and post-monsoon seasons had higher intestinal parasite prevalence and load as compared with pre-monsoon season. Thus, group size and intestinal parasites of Indian peafowl have an inverse relationship across seasons. Parasite load was significantly greater at food provision sites as compared with non-provision sites while parasite prevalence was comparable. Aggregation of individuals at the food provision sites may influence the parasite transmission and group-size dynamics in Indian peafowl. In conclusion, Indian peafowl are behaviourally plastic and fission-fusion of social groups may allow them to tackle ecological pressures such as predation and parasite transmission in different seasons.

We described the spatial segregation of two species of cetaceans, the common dolphin and the bottlenose dolphin. We also document the first direct observation of interspecific killing of a common dolphin by bottlenose dolphins and of interspecific necrophilia in cetaceans. The study was conducted from 2014 to 2019 in the Ría de Arousa (Northwest Spain). This study highlights that both species use this area as a foraging ground, although they show different patterns of occurrence (bottlenose dolphins were always observed in the ria and common dolphins were mostly observed outside). During the study period, bottlenose dolphins and common dolphins were only observed on five occasions at the same time and in the same area, including three occasions which led to the displacement of the common dolphin(s), and one lethal interaction. In this event, several bottlenose dolphins, including adults and calves, and males and females, aggressively herded, chased, and assaulted a common dolphin. After approximatively 10 min, the common dolphin corpse appeared floating at the surface, and several adult male bottlenose dolphins repeatedly pushed the body underneath the water surface and an (attempted) copulation was witnessed. We suggest that the common dolphin could have been killed for competition for food resources or practice for infanticide, and sexual arousal might have been triggered by expression of dominance. Further information about the occurrence of such behaviors, and the outcomes through specific studies on fitness would be crucial to further understand the implication of such events.

We report an observation at Jhalana Leopard Reserve (JLR), Jaipur, India. On 16 March 2019, we saw a female walking up the mountain while calling her two, 4-month-old, male and female cubs. This allowed several safari jeeps to park in the shade of nearby Acacia trees. Two Striped Hyenas (Hyaena hyaena) approached and sniffed at the base of one of the trees near the parked jeeps. Upon seeing the Hyaenas, the female ran down the mountain, passed between the jeeps, and climbed into the tree. That is when we noticed the body of the female cub at a height of approximately 4.5 m. The female licked the body of the cub for several minutes and then picked it up in her mouth, climbed down from the tree, passed again between the jeeps, and walked up the mountain towards a dense stand of Thor (Euphorbia caducifolia), a thorny cactus. Our observations display how a mother leopard that has lost a cub refuses to abandon the carcass, cached it in a tree, and when discovered by scavengers removed it to a thicket of cacti. We consider the behavior towards her dead cub, and subsequent caching when discovered by other animals, to be the first evidence for thanatological expression in leopards.

Providing artificial eggs is a commonly used technique to understand brood parasitism, mainly by the common cuckoo (Cuculus canorus). However, the presence of a cuckoo egg in the host nest would also require an earlier physical presence of the common cuckoo within the host territory. During our study of the red-backed shrike (Lanius collurio), we tested two experimental approaches: (1) providing an artificial “cuckoo” egg in shrike nests and (2) additionally placing a stuffed common cuckoo with a male call close to the shrike nest. We expected that the shrikes subject to the additional common cuckoo call stimuli would be more sensitive to brood parasitism and demonstrate a higher egg rejection rate. In the years 2017–2018,  in two locations in Poland, a total of 130 red-backed shrike nests were divided into two categories: in 66 we added only an artificial egg, and in the remaining 64 we added not only the egg, but also presented a stuffed, calling common cuckoo. Shrikes reacted more strongly if the stuffed common cuckoo was present. However, only 13 incidences of egg acceptance were noted, with no significant differences between the locations, experimental treatments or their interaction. Analysis of breeding success revealed significant differences between the locations, between experimental treatments and their interaction, which suggests a strong location effect. The red-backed shrike is an efficient rejector of foreign eggs. It would be interesting to see how similar tests affect hosts that have much higher rates of brood parasitism and egg acceptance.

Prey animals must balance the benefits of foraging in a particular area with their risk of predation in that area and often prioritize indirect cues to predation risk over direct cues of predators when making decisions about foraging under the risk of predation. Researchers using giving-up density (GUD) as a metric to assess perceived predation risk have found that it is affected by microhabitat, with certain animals willing to spend more time foraging (i.e., lower GUD) in relatively dense microhabitats and less time foraging (i.e., higher GUD) in relatively open microhabitats. This phenomenon has been attributed to those animals perceiving less predation risk when near or under shelter. However, the measurement has often confounded microhabitat density with distance from shelter in species without conspicuous dens. We measured GUD in foraging small mammals while experimentally manipulating microhabitat density and controlling for spatial location of the forager. Small mammals increased foraging (i.e., decreased GUD) as expected when we increased microhabitat density, but they did so despite those manipulations being randomly permuted spatially over the course of four rounds of data collection. Our results indicate that experimentally controlling for the potentially confounding effect of the forager’s distance to a safe location, such as dens, nests, or other shelters, did not remove the effect of microhabitat density on perceived predation risk. Thus, our results suggest that an animal’s perception of risk is likely mediated by both their location in their home range and the microhabitat at that location. We provide suggestions for further work.

Most triatomine bugs (Hemiptera: Reduviidae: Triatominae) are hematophagous, though Belminus species can live off of cockroach hemolymph to complete their life cycle. In this work, we described the fixed action pattern (FAP) employed by B. ferroae to identify, approach, and suck on a living cockroach. The FAP described here is composed of the following stereotyped behaviors: (1) visual and/or olfactory detection of the cockroach, (2) reaching, (3) cautious approach, (4) antennal exploration, (5) extension of the proboscis, (6) piercing to sedate, (7) walking away and waiting (postsedation behavior), (8) second cautious approach, (9) extension of the proboscis, (10) piercing to suck hemolymph. The FAP sequence observed suggests that Belminus bugs are not predators like the rest of reduviids (assassin bugs)—but are kleptophagous ectoparasites, since they do not attack and kill a prey but rather steal hemolymph from its invertebrate host. Based on these ethological observations, we propose kleptophagy as a trait that naturally groups the Belminus species into the Triatominae subfamily. In order to identify chemicals cues that could elicit such FAP, we examined the behavior of B. corredori, B. ferroae, and B. herreri in response to the cockroaches’ odor, fresh cockroach feces and fresh rodent wastes. The last two sources were tested based on the assumption that abundant chemicals near host refuges could serve as cues for host orientation. We found that the cockroach odor emanating from a box significantly attracted B. corredori and B. herreri in a still air olfactometer. The three Belminus species approached the captive cockroach after 1 h, but avoided to climb the box. Odors emanating from the cockroach feces attracted B. corredori and B. ferroae in a Y-olfactometer. Triatomines and their hosts have intimately shared the same refuge for millions of years; certain molecules occur across invertebrate and vertebrate refuges and are recurrent in human abodes, thus plausibly explaining how these bugs can readily switch to the domestic habitat, while keeping with their kleptophagous nature.

Across animal taxa, females of non-territorial species have potential opportunities to mate with multiple partners; hence, the primary mechanism available for males to ensure paternity is to guard the receptive female after copulation and repel other males. Hypothetically, mate-guarding is costly for males in terms of energy acquisition and increased risk of injury, and beneficial for females in terms of decreased harassment by other males and an increase in available foraging time. Here, we provide a detailed description of mating behavior and test these hypotheses in the Spix’s Whiptail (Ameivula ocellifera). Mating behavior is characterized by the following events: (1) a male courts a female in the entrance of her burrow; (2) if courtship is accepted by the female, a consensual copulation occurs; (3) after copulation the male accompanies the female during her daily activity, being aggressive towards other males; (4) when the female returns to the burrow, the companion male remains vigilant at the entrance and repels rival males. Besides the mate-guarding strategy, alternative mating tactics are adopted by some males that do not guard females after courtship and consensual copulation, while others try to copulate opportunistically with a female without prior courtship. Companion males spent more time vigilant, less time actively foraging, and captured less prey when compared to solitary males. Accompanied females captured prey in a similar proportion to solitary females but spent more time vigilant and less time foraging. Companion males won 100% of their interactions with rival males, chasing them away from the females. Accompanied females hence did not suffer harassment from other males when companion males were close. Our results evidence energetic costs of mate-guarding for males but not increased risk of injuries. By accepting mate-guarding, females do not appear to have energetic gains and lose the advantage of cryptic mate choice but can benefit from access to high-quality males and protection from harassment.