Fish odour triggers conspecific attraction behaviour in an aquatic invertebrate

Group living has evolved as an adaptation to predation in many animal species. In a multitude of vertebrates, the tendency to aggregate varies with the risk of predation, but experimental evidence for this is less well known in invertebrates. Here, we examine the tendency to aggregate in the freshwater amphipod Gammarus pulex in the absence and presence of predator fish odour. Without fish odour, the gammarids showed no significant tendency to aggregate. In contrast to this, in fish-conditioned water, they significantly preferred to stay close to conspecifics. Predation risk can, thus, influence gammarids social behaviour.     

Behavioural development of conspecific odour preferences in bank voles,Clethrionomys glareolus

Biological odours of conspecifics are known to have strong influences on behavioural interaction in bank voles Clethrionomys glareolus. This experiment tested two hypotheses. (1) Olfactory cues from familiar and unfamiliar mature opposite-sex conspecifics differ in their attractiveness to males and females, and their behavioural reactions change with age. (2) A genetically based mechanism is involved in female recognition of kin.In a two-choice preference test, prepubertal males and females were more attracted to familiar than to unfamiliar odours of opposite-sex conspecifics, as manifested by more time spent sniffing familiar voles. As the young reached sexual maturity they shifted their odour preferences. Mature males and females preferred the novel odour of unrelated opposite-sex conspecifics to that of relatives. The results of experiments testing the second hypothesis indicate that females use a genetically based mechanism to recognise their kin. Young and mature females were able to recognise the odour of their biological but socially unknown fathers, and showed the same pattern of behaviour as females in previous experiments.The possible biological functions of kin recognition in bank voles are discussed.     

The smell of cooperation: rats increase helpful behaviour when receiving odour cues of a conspecific performing a cooperative task

Reciprocity can explain cooperative behaviour among non-kin, where individuals help others depending on their experience in previous interactions. Norway rats (Rattus norvegicus) cooperate reciprocally according to direct and generalized reciprocity. In a sequence of four consecutive experiments, we show that odour cues from a cooperating conspecific are sufficient to induce the altruistic help of rats in a food-exchange task. When rats were enabled to help a non-cooperative partner while receiving olfactory information from a rat helping a conspecific in a different room, they helped their non-cooperative partner as if it was a cooperative one. We further show that the cues inducing altruistic behaviour are released during the act of cooperation and do not depend on the identity of the cue provider. Remarkably, olfactory cues seem to be more important for cooperation decisions than experiencing a cooperative act per se. This suggests that rats may signal their cooperation propensity to social partners, which increases their chances to receive help in return.     

Behavioural development of conspecific odour preferences in Brandt’s voleMicrotus brandti

The behavioural development of conspecific odour preferences in Brandt’s voleMicrotus brandti (Radde, 1861) was evaluated in laboratory tests. During the weaning period (15th-30th day after the birth), the preference of pups to individual odours of their parents, novel adult males and females were examined. Pups investigated odours of unfamiliar adults significantly more than those of their parents and they displayed significantly more jumping and upward visual investigating behaviours on the bedding soiled by unfamiliar adults than they did on the bedding of their parents. However, the frequency of crossing the parent’s bedding was significantly higher than the frequency of crossing the bedding of alien adults. It is suggested that odour discrimination ability was associated with the age of pups. The Brandt’s vole pups might keep themselves away from unfamiliar environments by keeping away from the novel conspecific odours.     

Effect of local spatial plant distribution and conspecific density on bumble bee foraging behaviour

1. Size variations in pollinator populations may modify competitive interactions among foragers. Competition among pollinators has been shown to lead to one of two contrasting behaviours: either specialisation to the most profitable plant species or generalisation to several species. When foraging, pollinators are also confronted with heterogeneity in the spatial distribution of plant resources. Because variations in both the forager density and plant spatial distribution can affect pollinator behaviour, focus was on the interactive effect of these two factors. 2. Bumble bee (Bombus terrestris L.) individuals were trained on a focal species (Lotus corniculatus L.) and experimentally tested whether variations in the forager density (two or six bumble bees foraging together), plant community spatial distribution (two plant species: L. corniculatus and Medicago sativa, which were either patchily or randomly distributed), and their interaction modified bumble bee foraging behaviour. 3. It was shown that when confronted with a high forager density, bumble bees focused their visits towards the most familiar species, especially when foraging under a random plant distribution. These modifications affected the fruiting of the focal plant species, with a significantly lower reproductive success under low density/patchy conditions. 4. This study demonstrates that the foraging decisions of bumble bees are influenced by variations in both the conspecific density and plant spatial distribution. Given the increasing impact of human activities on plant‐pollinator communities, this raises the question of the potential implications of these results for plant communities in natural conditions when confronted with variations in the pollinator density and spatial distribution of plants.     

Effect of host plant odour on the behaviour of the adult cabbage root fly, Erioischia brassicae

Laboratory experiments showed that the odour of leaves of host plants stimulated an increase in activity in gravied female E. brassicae while the odour of non-host foliage had little effect. Males and non-gravid females showed very little response to the odour of both types of foliage. Other experiments failed to show any orientation of the flies towards sources of host plant odour, although more flies were caught in traps containing the juice expressed from a host plant than in those containing water. It is suggested that an unoriented activation of gravid female E. brassicae by host plant odour enhances their chance of being caught in traps emitting the odour, and of making contact with host plants in the field.

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Zusammenfassung Laborversuche zeigten, daß der Blattduft der Wirtspflanzen die Aktivität der trächtigen Weibchen von Erioischia brassicae steigert, während der Duft von Fremdlaub nur einen geringen Effekt hervorrief. Die Reaktion der männlichen und der jungen weiblichen Tiere auf den Duft beider Laubtypen war gleichmäßig schwach. Weitere Laborversuche zeigten keine Orientierung der Tiere auf die Quelle des Wirtspflanzenduftes, dennoch wurden mehr Tiere in Fallen gefangen, welche Wirtspflanzensaft enthielten als in solchen, die nur mit Wasser beschickt waren. Es wird angenommen, daß die trächtigen Weibchen von Erioischia brassicae durch den Wirtspflanzenduft unorientiert aktiviert werden und somit für sie eine grössere Möglichkeit besteht, in Fallen gefangen zu werden, die einen solchen Duft ausströmen, und in der Natur auch mit Wirtspflanzen in Kontakt zu kommen.

     

Effect of conspecific alarm calls in the parental behaviour of nesting southern house wrens

Alarm calls are usually used to signal the presence of a threat to members of the same species and have been studied broadly in social foraging species. We analysed the effects of conspecific alarm calls on the parental behaviour of a territorial species, the southern house wrens (Troglodytes aedon musculus), during nestling stage. We compared the parental response of adults feeding 9–11-day-old nestlings when faced with conspecific alarm calls and with a control non-sympatric species’ song broadcast from a neighbouring territory. We measured the time required by parents to return to the nest (latency) when exposed to the stimuli and estimated parent’s nest visitation rate and mean visit duration. Parents took longer to resume parental activities when we broadcast a conspecific alarm call, but they did not modify their nest visitation rate or the mean visit duration. Heterospecific songs did not seem to affect parental behaviour. Our results suggest that nesting southern house wrens can use alarm calls uttered from neighbouring territories to assess the presence of a threat and adjust their parental behaviour accordingly.     

Effect of the odour of vaginal secretion on non-copulatory behaviour of male hamsters (Mesocricetus auratus)

Male hamsters were exposed to female vaginal secretion (in the absence of the female). When subsequently tested with females, their behaviour was determined by whether the test female matched or did not match the vaginal secretion. Less time was spent with mismatching females and less sniffing and licking was directed towards them. The effect of vaginal odour was present up to 3–4 h after the last contact with the secretion. The number of encounters with the vaginal odour and the spacing between them was important in determining the response to mismatching females. Contact with the vaginal secretion as opposed to its volatile components alone was necessary for the discrimination to occur. Discussion centres around the role of the vomeronasal organ and possible physiological pathways underlying the effect.     

Effects of litter size, age of young, and parity on foster mother behaviour in Rattus norvegicus

Maternal behaviour in the presence of newborn pups is determined by the age and size of the litter independent of parity of the mother, previous experience with different sized litters, and the number of days after delivery the measurements are taken. After fostering 10-day-old young, maternal behaviour is influenced by the age and size of the litter and also by the mother's previous experience with different sized litters.     

Denning behaviour of ship rats (Rattus rattus) on Taukihepa,a seabird breeding island

Abstract

Den sites of 14 ship rats (Rattus rattus) were located daily during the rat breeding season on Taukihepa (Big South Cape), a seabird island southwest of Rakiura (Stewart Island). In contrast to other New Zealand studies, no arboreal dens were found. Den sites on Taukihepa were in ferns, under logs, in woodpiles, or underground in sooty shearwater (Puffinusgriseus) breeding burrows. The number of times known den sites used was positively related to the amount of leaf litter and woodpiles near the den sites. Overall, 24% of radio‐tagged rats were sharing den sites on any given day. While there was considerable individual variation in the number of times den sites were used, female rats tended to reuse den sites more than males. Many rats were found in dens alone, but frequently males and females shared. Occasionally two females and one male denned together, as did two females, whereas males never denned with another male.     

Flight behaviour of tsetse flies in host odour plumes: the initial response to leaving or entering odour

ABSTRACT. Free-flying, wild male and female Glossina pallidipes Aust. and G. m. morsitans Westw. were video-recorded in the field in Zimbabwe as they entered or left the side of a host-odour plume in cross-wind flight, or as they overshot a source of host odour in upwind flight (camera 2.5 m up looking down at a 3 times 2.5 m field of view at ground level). 80% of cross-wind odour leavers turned sharply ( turns 95^o), but without regard to wind direction (overshooters behaved essentially the same except that nearly 100% turned). Many fewer flies entering a plume cross wind turned ( c . 60%), and when they did they made much smaller turns ( 58^o); these turns were, however, significantly biassed upwind ( c . 70%). All three classes of fly had similar groundspeeds ( 5.5–6.5 m s^_1) and angular velocities ( 350–400^o s^-1). Clear evidence was obtained of in-flight sensitivity to wind direction: significantly more flies entering odour turned upwind than downwind, and odour losers turning upwind made significantly larger turns than average. The main basis for the different sizes of turn was the different durations of the turning flight, rather than changes in angular velocity or speed. No evidence was found of flies landing after losing contact with odour.     

Searching behaviour of the sevenspotted ladybird, Coccinella septempunctata– effects of plant-plant odour interaction

In the present study the main aim was to investigate the odour mechanisms affecting habitat preferences of Coccinella septempunctata (L.). In a field study, the frequency of adult C. septempunctata was higher in barley plots containing high densities of the common weeds Cirsium arvense (L.) Scop. and Elytrigia repens (L.) Nevski. than in control plots with only barley. In olfactometer experiments in the laboratory, adult C. septempunctata showed a significantly more positive response to mixed odours of barley and each of the two weeds than to barley alone. Ladybirds responded differently to barley plants that were previously exposed to volatiles from the two weeds. The E. repens -exposed barley plant lost its attractivity while the C. arvense -exposed barley plants maintained attractivity. As no aphids or pollen resources were present in the plots during the experiment, the results show that C. septempunctata responds to the botanical characteristics of the habitat even if no food resources are available. These results strongly suggest that olfactory cues and plant-plant communication from diversified plant stands can be important mechanisms in predator attraction to sites with a complex botanical diversity.     

Factors affecting the response of Ceutorhynchus assimilis Payk. (Col., Curculionidae) males to conspecific odour

The effect of post-emergence feeding on the response of Ceutorhynchus assimilis males to conspecific odour was studied using both laboratory-overwintered and field-collected weevils. The response of males to females at different times in the season was also investigated using field-collected weevils. Males did not respond to the odour of virgin females that were newly emerged from diapause. However, they showed a significant response to the odour of overwintered virgin females that had spent some days on flowering rape. The response of males to females appeared to decline as the season progressed.     

Effect of conspecific attraction on the presence of Northern Bobwhites

Researchers and managers have used the tendency of some species of birds to settle near conspecifics (i.e., conspecific attraction) to help establish or reestablish species of conservation concern in targeted habitats. However, most studies of conspecific attraction as a recruitment tool have been conducted with either migratory or colonial-breeding species, and less is known about the possible importance of conspecific attraction for resident species. In 2017 and 2018 in Louisiana, we examined the possible use of conspecific attraction as a management tool for Northern Bobwhites (Colinus virginianus), game birds that are year-round residents. We used an alternating split experimental design across years where Northern Bobwhite vocalizations were broadcast at half of our study sites during the first year of our study and the other half were controls. The following year, experimental sites became controls, and controls became experimental sites. We also assessed land cover at each site to determine if variation in habitat composition at small spatial scales influenced bobwhite presence. We detected six times more Northern Bobwhites at treatment sites (sites with playback) than control sites and found a positive association between the proportion of grass cover and bobwhite presence. These results suggest that a non-migratory, resident species may select breeding locations based, at least in part, on the presence of conspecifics, and that playback of their calls could be incorporated into management plans. Playing back conspecific calls in early spring when Northern Bobwhites are likely searching for breeding locations may facilitate colonization and allow individuals to find locations where managers are attempting to restore their populations.     

Scent-marking behaviour in response to conspecific odours by the rat, Rattus norvegicus

The scent-marking behaviour of male and female rats in response to conspecific odours was investigated in two experiments. The results of the first experiment indicated that exposure to conspecific odours generally led to an increase in marking rates. However, no sex differences were found, and large differences in marking responses according to the sex of the odour donor were only found for dioestrous females. These results do not suggest that the primary function of scent-marking in this species is sexual. In the second experiment, odour sources differed not only in the sex of the donor, but also in their relative familiarity to the animal being tested. This experiment showed that males marked more in response to odours from familiar (non-related) females. Females did not differ significantly on measures of marking but did display greater interest in odours from unfamiliar males. The results are discussed in relation to possible functions of marking in this species.     

Olfactory experience modifies the effect of odour on feeding behaviour in a goal-related manner

Natural food odours elicit different behavioural responses in snails. The tentacle carries an olfactory organ, and it either protracts toward a stimulating carrot odour or retraces in a startle-like fashion away from a cucumber odour. The tentacle retraction to cucumber was still present after the snails were fed cucumber during inter-trial periods. Also, snails without any food experience displayed a longer latency to the first bite of cucumber than of carrot and rejected cucumber more often. After tasting these foods, the latency to carrot was not affected while the latency to and number of rejections of cucumber decreased. These results suggest that initial repulsive features of food odour can be only partially compensated by olfactory learning and feeding experience. In the present study, we demonstrated that an invertebrate can be repulsed or attracted by the same natural odour at the same time and that these behavioural responses are likely aimed at achieving different physiologically relevant goals.