Intact Conspecifics Research Articles

Rat ultrasonic vocalizations and novelty-induced social and non-social investigation behavior in a seminatural environment

Although rats are known to emit ultrasonic vocalizations (USVs), it remains unclear whether these calls serve an auditory communication purpose. For USVs to be part of communication, the vocal signals will need to be a transfer of information between two or more conspecifics, and with the possibility to induce changes in the behavior of the recipient. Therefore, the aim of our study was to investigate the role of USVs in adult rats’ social and non-social investigation strategies when introduced into a large novel environment with unfamiliar conspecifics. We quantified a wide range of social and non-social behaviors in the seminatural environment, which could be affected by subtle signals, including USVs. We found that during the first hour in the seminatural environment the ability to vocalize did not affect how quickly adult rats met each other, their overall social investigation behavior, their passive social behavior nor their aggressive behavior. Furthermore, the non-social exploratory behaviors and behaviors reflecting anxiety/stress-like states were also unaffected. These results demonstrated that a disability to vocalize did not result in significant disadvantages (or changes) compared to intact conspecifics regarding social and non-social behaviors. This suggests that other (multi)sensory cues are more relevant in social interactions than USVs.

Social proximities of developing gorilla males (Gorilla gorilla gorilla) in European zoos: The consequences of castration and social composition

In the European captive population of western lowland gorillas (Gorilla gorilla gorilla), the harem social structure and an even sex ratio at birth result in a surplus of males and consequent management difficulties. This study seeks to assess the socialization differences between captive juvenile and adolescent male gorillas according to their fertility status (intact vs castrated) in different social compositions (familial vs bachelor groups), and to evaluate the suitability of castration as a management tool for the EEP gorilla population. We carried out social network analyses (SNA) to assess the “positive” proximity pattern of behaviour in 93 western lowland gorillas aged from 0 to 45 years old and housed in 11 social units (seven familial and four bachelor groups). We compared the data recorded for the 27 juvenile and adolescent (i.e. subadult and blackback) males included in our sample size. Although no differences were revealed between the intact juveniles and the castrated juveniles living in familial groups, our results showed that castrated adolescent individuals showed more cohesiveness within their familial group than their intact conspecifics in terms of their activity budget. They also displayed a “positive” proximity pattern of behaviour with all group members, including adults (silverback and females). Despite being significantly more isolated, the intact adolescent males living in bachelor groups do not differ from their castrated and intact counterparts of the same age class living in familial groups in terms of their strength of “positive” behaviour when close to group conspecifics. This effect highlights the social benefits of male-male interactions within gorilla species. Our results may be evidence that both of the management strategies compared here, i.e. bachelor groups and castration, could be appropriate socio-behavioural enrichments during juvenility and adolescence. These findings also highlight the need to continue investigations until the study subjects reach adulthood to validate and/or improve these tools for the welfare-compliant management of gorilla male surplus in captivity.

Length of time domestic dogs (Canis familiaris) spend smelling urine of gonadectomised and intact conspecifics

Domestic dogs (Canis familiaris) use urine to communicate among themselves, however, it is unknown whether the gonadectomy (neutering or spaying) of a dog affects this communication in anyway. Urine samples from 10 intact and 10 gonadectomised, unfamiliar dogs were presented to 12 tester dogs to sniff under controlled conditions in a pilot study. The amount of time the tester dogs spent sniffing each sample was recorded. Overall, tester dogs were recorded smelling the urine of gonadectomised individuals for a longer time. In addition to the type of urine sample, the result is likely to have been influenced by the sex and status (gonadectomised or intact) of the tester dogs. The observed increase in the length of time spent sniffing urine from gonadectomised individuals could be explained by the tester dogs experiencing more difficulty in gaining information from the urine or facing more confusion while analysing the urine compared to the intact urine they have evolved to smell.

Damage and physiological stress to juvenile eastern rock lobster (Sagmariasus verreauxi) discarded after trapping and hand collection

Large numbers of Sagmariasus verreauxi are trapped and hand collected in Australia, but discarded due to size and quota restrictions, and under the unevaluated assumption of few impacts. To test the validity of enforced discarding, trapped and hand-collected S. verreauxi (49–143mm carapace length – CL) were examined for external damage, placed into cages, transferred to aquaria and monitored (with controls) over three months. Haemolymph was non-repetitively sampled immediately and at one, three, and seven days to quantify stress. Most trapped (64%) and hand-collected (79%) specimens were undersized (<104mm CL), with the latter method yielding broader ranges of sizes and moult stages. Within-trap Octopus tetricus predation caused the only mortalities (3.3%). Hand collection resulted in much greater antennae and pereopod loss than trapping (53 vs. 4%) but, compared to controls, both methods evoked benign physiological responses that resolved within a week. While most wounded S. verreauxi regenerated all or some missing appendages post-moult, their mean CLs were less than those from intact conspecifics. Simple strategies, including larger mesh sizes, and/or installing modifications to reduce bycatch in traps, careful hand collection, and appropriate release techniques might minimise impacts (including predation) to unwanted S. verreauxi, and help to control stock exploitation.

Diamondback moth oviposition: effects of host plant and herbivory

AbstractThe oviposition behaviour of Plutella xylostella L. (Lepidoptera: Plutellidae) on Chinese cabbage (Brassica rapa L. Pekinensis, cv. Wombok), canola (Brassica napus L. cv. Thunder TT), and cabbage (Brassica oleracea L. Capitata, cv. sugarloaf) (Brassicaceae) was studied in the laboratory. In no‐choice experiments moths laid most eggs on the stems and lower three leaves of cabbage plants, the lower three leaves of canola plants, but on the upper three leaves of Chinese cabbage plants. The effects of conspecific herbivore damage to foliage could be replicated by mechanical damage. When foliage was damaged, injured cabbage and canola plants were preferred for oviposition over intact conspecifics, whereas injured Chinese cabbage plants were less preferred than intact conspecifics. However, when root tissue was damaged, intact cabbage and canola plants were preferred over injured conspecifics, whereas moths did not discriminate between root‐damaged and intact Chinese cabbage plants. Injury to upper leaves significantly affected the intra‐plant distribution of eggs. In cabbage and canola plants, injury to leaf 6 significantly increased the number of eggs laid on this leaf, resulting in a significant decrease in the number of eggs laid on the lower foliage/stem of plants, whereas in Chinese cabbage plants it significantly decreased the number of eggs laid on leaf 6. Following oviposition on intact plants, neonate larvae established the vast majority of feeding sites on leaves 5–8 in all three host plants, indicating that larvae moved a considerable distance from preferred oviposition sites in cabbage and canola plants. The growth rate of neonates fed on leaf‐6 tissue was significantly greater than that of those fed on leaf‐1 tissue; &gt;90% of larvae completed development when fed exclusively on leaf‐6 tissue but no larvae completed development when fed exclusively on leaf‐1 tissue. The study demonstrates the complex and unpredictable interactions between P. xylostella and its host plants and provides a basis from which we can begin to understand observed distributions of the pest in Brassica crops.

Anti-predator behaviour in the green-lipped mussel Perna viridis: byssus thread production depends on the mussel’s position in clump

Green-lipped mussels Perna viridis secrete a larger number of byssus threads to anchor themselves to the substrate more firmly when predation risks are high. These mussels also form clumps. As predators usually attack clumps from the periphery, the predation risks of solitary mussels are higher than those of mussels living along the edge of clumps, which are in turn higher than those of mussels living within the clumps. The byssus thread number, length and diameter were investigated in relation to the mussels’ position in the clump. We set up chemical stimulus treatments with damaged conspecifics and heterospecifics, suggesting predation risks, as well as with intact conspecifics and heterospecifics, shrimp cues and control (no cue). The mean number of byssus threads produced was significantly affected by both the mussels’ position in the clump, the treatment type, and the interactive effect between these 2 variables. In the treatment in which mussels were exposed to damaged conspecific cues, the mean number of byssus threads produced by the solitary mussels was greater than the number produced by edge mussels, which was, in turn, greater than the number produced by the mussels within the clump. Furthermore, the solitary and edge mussels exposed to damaged conspecifics secreted more byssus threads than their counterparts in the control, intact conspecifics, intact and damaged heterospecifics, and shrimp meat treatments. However, the mussels within the clumps exposed to damaged conspecifics did not secrete more byssus threads than their control counterparts. Results of the present study suggest that the anti-predator responses to risk may be related to the presence of damaged conspecifics and the mussels’ position in the clump, both indicative of local predation pressure.

Marine mussels Brachidontes variabilis selected smaller places of refuge and enhanced byssus production upon exposure to conspecific and heterospecific cues

Refuge selection and byssus production as anti-predator responses were examined in mussels Brachidontes variabilis exposed to cues either released from damaged or intact conspecifics, from damaged or intact heterospecific mussels Perna viridis sympatric with B. variabilis or from shrimp meat as novel cues. Most of the mussels from all treatment groups would seek and stay in a refuge for the first few hours, with a significantly higher number of mussels from the damaged conspecific group seeking refuge. More mussels preferred a smaller refuge when they were exposed to conspecific or heterospecific cues; mussels from other treatments did not select particular sizes of refuge. Damaged conspecific and heterospecific cues elicited the greatest responses in byssus production with more byssal threads being produced, which were also longer and thicker. Novel cues elicited medium levels of response, suggesting that some common cues from injured or dead individuals from different taxa were released, which induced anti-predator responses in B. variabilis.

Spider mites assess predation risk by using the odor of injured conspecifics.

When a predatory mite, Amblyseius womersleyi is present, Tetranychus kanzawai takes refuge on its webs during a quiescent stage. To examine the factors responsible for the antipredator behavior of T. kanzawai, we exposed T. kanzawai to the odor of conspecifics, A. womersleyi, and both T. kanzawai and A. womersleyi. The proportion of T. kanzawai females that took refuge was significantly higher when they were exposed to the odor of 'both T. kanzawai and A. womersleyi.' Furthermore, the proportion of T. kanzawai females that took refuge was significantly higher when they were exposed to injured conspecifics than to intact conspecifics. These results suggest that T. kanzawai assesses predation risk, at least in part, by using the odor of injured conspecifics.

Direct and indirect cues of predation risk influence behavior and reproduction of prey: a case for acarine interactions

Little is known about the flow of chemical information from higher to lower levels within the animal food chain. However, this information may determine the behavior and distribution of many animals (e.g., that of potential prey) when exposed to direct and indirect cues of predation risk. We used herbivorous spider mites, Tetranychus urticae Koch (Tetranychidae) as a model to examine the foraging and oviposition decisions that prey make when exposed to these cues. We conducted laboratory tests to determine if the previous presence of predators (direct cues) on leaf discs or the presence of injured conspecifics (indirect cues) alters the distribution of adults and eggs of T. urticae. When given a choice, after 24 h, fewer adults and eggs were found on leaf discs that had previously contained specialist spider mite predators, Phytoseiulus persimilis Athias-Henriot (Phytoseiidae), than on discs unexposed to predators. Also, more T. urticae emigrated from predator-exposed discs than from unexposed discs or from those that had previously contained nonpredatory mites (Tyrophagus putrescentiae, Acaridae). Finally, fewer T. urticae foraged and laid eggs on predator-exposed discs or on those with artificially damaged conspecifics (eggs or dead adults) than on discs with intact conspecifics. Tetranychus urticae probably recognizes infochemicals (kairomones) from its predators or cues from injured spider mites and consequently avoids feeding or ovipositing in areas exposed to these cues. Recognition and avoidance of kairomones from specialist predators by this prey are likely to be hereditary, but avoidance of injured conspecifics may be an adaptation to avoid predators that are not inherently recognized. We discuss the behavioral and ecological implications of our findings.

Behavioral responses ofLittoraria irrorata (SAY) to water-borne odors

Behavioral responses of the gastropod molluscLittoraria (=Littorina)irrorata indicate that it can discriminate among environmental odors. Snails were assayed for responses to 11 odors from plants and animals potentially representing food, shelter, location in the environment, and predators. Crushed conspecifics were included as an alarm odor. Except for odor of crushed conspecifics, all odor sources were water-borne from living intact organisms. Behavioral responses were categorized as no response, positive response, or negative response. For some analyses, negative responses were subdivided into withdrawing and turning responses. Snails responded positively to several plant odors. They did not respond to odors of intact conspecifics, fiddler crabs, or grass shrimp. They responded negatively to odors of a plant found at the upper limit of their minimal habitat, predatory blue crabs, crushed conspecifics, predatory gastropods, and ribbed mussels. Odors of blue crabs on different diets affect the type of negative response the snails display.

Interactions between bats and arctiid moths

Many arctiid moths emit trains of ultrasonic clicks upon tactile stimulation and when exposed to trains of ultrasonic pulses like those emitted by bats. We observed the responses of captive big brown bats (Eptesicus fuscus) and free-foraging red bats (Lasiurus borealis) to arctiid moths and similar-sized moths of other families, and the responses of free-flying moths to trains of ultrasonic pulses like those of bats. Both the big brown bats and the red bats ate significantly fewer arctiids than were available to them, but the captive bats were more likely to kill arctiids than were the free-flying ones. The captive bats ate fewer of the arctiids they killed than moths of other families. Muted arctiid moths were caught by the red bats more than intact conspecifics but usually were dropped without being eaten. Free-flying arctiid moths changed their flight paths less in response to trains of ultrasonic pulses than did moths of other families similarly capable of hearing these signals. These results suggest that arctiid moths use their clicks and chemical defenses to protect them from the bats that prey upon them, and that these clicks are aposematic signals that warn bats of unpalatable prey.

The attack frequency of Gnathonemus petersii towards electrically silent (Denervated) and intact conspecifics, and towards another mormyrid (Brienomyrus niger)

1. Aggression experiments were performed with Gnathonemus petersii. Three kinds of stimulus fish were used in random order to elicit attacks: (1) intact conspecifics, (2) electrically silent (operated) conspecifics, and (3) the mormyrid Brienomyrus niger. 2. The aggression indices for the two experiments with B. niger and the intact conspecific, i.e. the two electrically active fish, were similar (p<0.4), whereas the index for the experiment with the silent conspecific was about one half of the two others (p<0.01, Fig.2). 3. In none of the three experimental conditions can the behavior sequence displayed by G. petersii be described by a random model, i.e. the occurrence of a given act depended on at least the preceding act (p<0.001, Tables 1–3), as in a first-order Markov chain. For every behavior recognized, the distribution of following acts on a given act found in one group of experiments was significantly different from the same distribution found in one of the two other groups of experiments (Table 4). 4. The behavioral sequences, displayed by the experimental subjects, exhibited redundancies which were only slightly different when an intact (35%) or an electrically silent conspecific (33%) were present (Table 5). A considerable difference between both experiments was found on comparing the information T(x;y) which is common to a preceding behavior x and a following behavor y: in the silent conspecific experiment T(x;y) was more than twice the value found in the intact conspecific experiment (0.65 and 0.28 bit, respectively). In the B. niger experiment T(x;y) was found to be low (0.24 bit). In contrast to both conspecific series of experiments, the redundancy value was also low (23%). A high degree of redundancy of the behavioral sequence in spite of a low amount of internal constraint-both considered to be of prime importance in a communication system-were shown by the experimental G. petersii in the presence of intact conspecifics only. 5. There were considerable differences in the electrical discharge activities of B. niger and G. petersii (Figs. 4–6). B. niger did not display a Preferred Latency Response to G. petersii's pulses (Fig. 7). 6. The results show that by conspecific electric signals, information is transmitted which significantly influences the behavior of a recipient G. petersii. These signals seem to be strictly species-specific.

Effects of Day 1 castration on aggressive behaviors of rats

No rats killed mice in a group of adult male rats which had been castrated on the first day of life; in samples of intact adult males the percentages of killers were consistently between 20%-30%. The percentage of killers among females was slightly higher than in the castrated male group. Testosterone injections had a slight effect in that three castrates began to kill after adult treatment with TP. Electric shock failed to induce stereotyped attacks on mice in castrates, who were also reliably subordinate in shock-elicited fights with intact conspecifics.