No cultural transmission of species recognition between parents and offspring in free-living great tits and blue tits

Imprinting plays a key role in the development of species recognition, with young imprinting upon the morphological characters of their parents. However, the potential role that cultural transmission might play in species recognition remains largely uninvestigated. Great tits (Parus major) and blue tits (Cyanistes caeruleus) do not normally perceive each other as sexual competitors or potential partners. However, after reciprocal interspecific cross-fostering, both species may perceive individuals of the foster species as potential rivals or mates. Although the experience of being raised by heterospecifics clearly has affected the species recognition of cross-fostered birds, some of them breed naturally with conspecifics. The offspring of such cross-fostered birds (OCF) are hence raised by parents that look like ordinary conspecifics but display deviant species recognition as compared to controls in terms of aggressive response towards rivals. Comparing the aggressive behavior of OCF, cross-fostered birds and controls towards territorial intruders may thus help tease apart the influence of morphological vs behavioral cues of parents in the development of offspring species recognition. To this end, we compared birds from all three treatments with respect to their aggressive response to territorial intruders of both species during the breeding season. OCF and controls did not differ in their pattern of response towards heterospecific and conspecific stimuli. Compared to cross-fostered birds, OCF and controls showed less aggression towards heterospecific intruders, while the response towards conspecific intruders did not differ between treatments. These results demonstrate that both tit species imprint on the morphological characters of their parents, but that parental behavior is not important for the development of species recognition in terms of aggressive response towards territorial intruders.     

Dominions and site-fixed aggressive behavior in breeding male Leucorrhinia intacta (Odonata: Libellulidae)

Summary We report aggressive spacing behavior in male dragonflies, Leucorrhinia intacta, that is characterized by variations in the probability of chasing conspecific male intruders within a defined area around a male's perch. The chase probability depends on the total intruder pressure and the behavior and distance of the intruder from the perched male (Fig. 2). This nonexclusive, site-fixed area has been called a dominion.We also examined the distribution of intruders among the various behavior-distance categories. Chase rates (per 15 min) were correlated mostly with number of intruders that hovered (rather than flew) close to the territorial male. Finally, we examined the impact of the changing chase probabilities on the variation in aggressive interactions as a function of intruder pressure. We conclude that, to some extent, territorial males stabilized defense costs across a variety of intruder pressures by maintaining dominions.     

Influence of residency and social odors in interactions between competing native and alien rodents

Residency status of individuals in populations may be an important determinant of the outcomes of interspecific competition between native and introduced species. We examined direct behavioral interactions between two similarly sized rodents, the alien Rattus rattus and native Rattus fuscipes when they were respective residents and intruders in a small enclosure. Resident individuals were dominant in their behaviors toward intruders irrespective of the species that was resident. In contrast, interactive behaviors between conspecifics were often neutral or amicable, supporting suggestions that R. rattus and R. fuscipes are social animals. We then tested whether rodent species use heterospecific odors to avoid aggressive competitive interactions and partition space in the field. Neither R. fuscipes nor R. rattus responded to traps scented with the odors of male or female heterospecifics. If R. fuscipes does not recognize the odor of introduced R. rattus, then odors will not be cues to the presence or territorial space of competing heterospecifics. Rather, findings from both enclosure and field trials suggest that direct aggressive interactions between individual R. rattus and R. fuscipes probably facilitate segregation of space between these two species in wild populations, where resident animals may typically be the winners and exclude heterospecific intruders. These findings have implications for the invasion success of introduced rodents such as R. rattus into intact forests, where native populations may have competitive advantage because of their residency status.     

Species recognition and species isolation in wandering spiders (Cupiennius spp.; Ctenidae)

Summary One of the roles ascribed to spider courtship is that of mate recognition and reproductive isolation. We describe behavioral mechanisms underlying these functions in three species of wandering spiders of the genus Cupiennius (Ctenidae). C. salei and the two sympatric species C. getazi and C. coccineus discriminate conspecifics and heterospecifics in a multistage process which covers three principal phases of courtship: (1) Chemical phase: male spiders initiate vibratory courtship communication less often upon contact with heterospecific than with conspecific female silk. (2) Vibratory phase: females respond with their own vibration less often and with increased delay to the vibratory courtship signals of heterospecific males than to those of conspecific males. (3) Tactile phase: in heterospecific pairings males and females interrupt the contact phase if their courtship has progressed thus far. The product of the probabilities of passing through each of the different stages of courtship is between 0.44 and 0.88 for conspecific pairings, but zero for most heterospecific pairings. This is to a greater extent due to the behavioral barriers of the vibratory and the tactile phase than to that of the chemical phase. Male taxis on tracks of female silk does not depend on the species-specificity of the silk. Female vibrations are not essential for species recognition: males increase their signal rates, orient toward and approach responding females in both con- and heterospecific pairings. Female attacks on males are similar to attacks on prey; males defend themselves with outstretched front legs and are caught and killed by the female in only 5% of the cases. In all phases of courtship, female C. salei are least and female C. getazi most selective. When female C. coccineus and C. getazi are involved in heterospecific pairings no copulation is attempted. In contrast, 13 copulations of C. salei with males of the other two species were observed; egg sacs never resulted from these copulations. Among males, those of C. getazi were least selective. The likelihood of heterospecific pairs passing through all phases of courtship is higher in case of the allopatric than in that of the sympatric species. This finding applies to the courtship as a whole, but not necessarily to each of its phases.Offprint requests to: F.G. Barth     

Asexuals looking for sex: conflict between species and mate-quality recognition in sailfin mollies (Poecilia latipinna)

When two closely related species are sympatric the process of species recognition (identifying conspecifics) and mate-quality recognition (increased fitness benefits) can yield a conflict when heterospecifics resemble high-quality conspecifics. Conflict in species versus mate-quality recognition may serve as a possible mechanism for the persistence of unisexual, gynogenetic Amazon mollies (Poecilia formosa). Amazon mollies require sperm from closely related species (e.g., sailfin mollies, P. latipinna) to start embryogenesis but inheritance is strictly maternal. When choosing mates, male sailfin mollies from populations sympatric with Amazon mollies may rely on traits indicating species identity rather than those indicating mate quality. Conversely, males from allopatric populations may rely more on traits indicating mate quality. Previous work has found that male sailfin mollies in sympatry exhibit a significantly greater mating preference for female sailfin mollies over Amazon mollies compared to males in allopatry. In addition, male sailfin mollies prefer to associate with and produce more sperm in the presence of larger conspecific females, which are more fecund. We hypothesized that male sailfin mollies experience a conflict in species recognition and mate-quality recognition in the presence of Amazon mollies that are relatively larger than female sailfin mollies. To test this hypothesis, we paired males from sympatric and allopatric populations with a larger Amazon molly and a smaller female sailfin molly. We scored the number of mating attempts that males directed to conspecific and heterospecific females. Males in most sympatric and allopatric populations demonstrate no clear preference for conspecifics. In addition, we found some evidence for a difference in mating preference between allopatric and sympatric populations with males from allopatry showing a greater heterospecific mate preference. These results indicate a conflict between species and mate-quality recognition. In sympatry this conflict may contribute to the persistence of gynogenetic Amazon mollies.     

Fluctuating asymmetry,interspecific aggression and male mating tactics in two species of Japanese scorpionflies

Summary Fluctuating asymmetry (FA) is defined as small, random deviations from bilateral symmetry in a generally perfect bilaterally symmetrical morphological trait. FA in forewing length affects the outcomes of interspecific contests for food items (dead arthropods) between two species of Japanese scorpionflies, Panorpa nipponensis and P. ochraceopennis, in nature. FA differences between same-sex contestants are more important than either body size or ownership of food in determining the outcomes of interspecific contests; for both sexes, winners statistically significantly more often have relatively low FA. Two condition-dependent mating tactics are used by the males of each species: (a) a male may defend a dead-arthropod nuptial gift, or (b) a male without such an arthropod may wait near a male with one. In both tactics, males release long-distance sex pheromones. Groups of pheromone-releasing males are made up of one male with a nuptial gift and his satellites; the males in a group may be conspecifics or heterospecifics. Males that lose contests for nuptial gifts often become satellites of the contest winners whether or not winners are conspecific. Satellite males have statistically significantly greater FA than males with nuptial gifts in heterospecific male display groups. Satellite males mate infrequently and briefly compared to resource-holding males. Satellites of heterospecific males copulate with conspecific females displaced from nuptial gifts by the resource-holding males of the other species. In both species, the largest and smallest individuals have the greatest FA, and intermediate-sized individuals have the least; this same pattern often occurs in other animals.     

Behavioral responses to echolocation calls from sympatric heterospecific bats: implications for interspecific competition

Mutual recognition is the product of species coexistence, and has direct effects on survival and reproduction of animals. Bats are able to discriminate between sympatric different heterospecifics based on their echolocation calls, which has been shown both in free-flying and captive bats. To date, however, the factors that may determine the behavioral responses of bats to echolocation calls from sympatric heterospecifics have rarely been tested, especially under well-controlled conditions in captive bats. Hence, we aimed at tackling this question by performing playback experiments (habituation–dishabituation) with three horseshoe bat species within the constant-frequency bat guild, which included big-eared horseshoe bats (Rhinolophus macrotis), Blyth’s horseshoe bats (Rhinolophus lepidus), and Chinese horseshoe bats (Rhinolophus sinicus). We studied the behavioral responses of these three species to echolocation calls of conspecifics, to other two species, and to another heterospecifics bat, Stoliczka’s trident bat (Asellisus stoliczkanus), which also belongs to this guild. We found that the three rhinolophid species displayed a series of distinct behaviors to heterospecific echolocation but few to conspecific calls after habituation, suggesting that they may have been able to discriminate sympatric heterospecific echolocation calls from those of conspecifics. Interestingly, the behavioral responses to heterospecific calls were positively correlated with the interspecific overlap index in trophic niche, whereas call design had only a minor effect. This implies that the behavioral responses of these bats to heterospecific echolocation calls may be related to the degree of interspecific food competition.     

Territory ownership and familiarity status affect how much male root voles (Microtus oeconomus) invest in territory defence

Neighbour–stranger discrimination occurs when individuals respond with more aggression to strangers than to territorial neighbours—a phenomenon termed the “dear enemy phenomenon” (DEP). We investigated the DEP with male and female root voles (Microtus oeconomus Pallas 1776) using field dyadic arena tests conducted in enclosures where we could test for the effects of familiarity (familiar versus stranger), ownership (resident versus intruder status) and resource-holding potential (body mass) on territorial behaviours. The results showed that males put more effort into territorial defence than females, and males could discriminate between neighbours and strangers. In males, aggressiveness was influenced by a significant two-way interaction between treatment and ownership. Male residents were more aggressive towards stranger intruders than towards neighbour intruders, while male intruders were less aggressive towards stranger residents than towards neighbour residents. In females, neither treatment nor ownership status had a significant effect on aggressiveness. Familiar males performed more social behaviours but less non-social behaviours than stranger males. Furthermore, there was a clear dominance hierarchy between residents and intruders in stranger dyads, with the male territory holders dominating the intruder in pairwise interactions. To our knowledge, these results demonstrate for the first time DEP in a small mammal with a known pedigree and present the first evidence for “prior resident advantage” in voles. We argue that both ownership status and familiarity status affect how much an individual invests in territory defence. The benefits of neighbour–stranger discrimination for male root voles and the absence of neighbour–stranger discrimination in female root voles are discussed.     

Aggressiveness of breeding territorial honeyeaters corresponds to seasonal changes in nectar availability

Summary On the east coast of Australia, new holland and white-cheeked honeyeaters experience huge seasonal changes in nectar availability over their breeding periods. I observed breeding males of both species to determine whether levels of territorial aggressiveness varied with these changes in nectar availability. I watched individual males repeatedly and assessed their aggressiveness by recording their responses to birds that came within 30 m of them. Almost all attacks were on unfamiliar birds; males never attacked their mates or offspring and rarely attacked other birds that were resident in the area. Intruders were most likely to be attacked if they were conspecifics, if they landed rather than flying by, and if they came near the centers of males' territories. Taking into account the types, behaviors, and locations of intruders, there were pronounced seasonal changes in the probability of an intruder being attacked by a territorial male. Males were least aggressive when nectar was abundant, suggesting that territorial aggression could be at least partially a response to scarcity of nectar. Seasonal changes in aggressiveness were not accounted for by breeding cycles or by changes in frequency of intrusions.     

Seasonal variation in territorial response,and other aspects of the ecology of the Australian temperate pomacentrid fish Parma microlepis

The Australian temperate pomacentrid fish Parma microlepis Gunther maintains permanent, interspecifically defended territories. Breeding occurs in late spring (October to December), and juveniles after a pre-settling period of 4 to 6 weeks take up territories in the adult habitat. P. microlepis feed in their territories on benthic algae and invertebrates. Density of fish is significantly correlated with the availability of suitable shelter. There is a variation in the territorial response directed at different species, and a significant correlation exists between intensity of response to a species and its similarity to P. microlepis in use of living space. No significant correlation exists between intensity of response and dietary similarity. P. microlepis defends larger areas in the breeding than in the non-breeding season against those species which represent a possible threat to its breeding success. It shows a reduced tendency to attack juvenile conspecifics at the time of year when they would be settling from the plankton. Responses to species not likely to interfere with breeding success do not vary through the year. P. microlepis is thus seen to have complex territorial responses, specific to the species of intruder and time of year. In this it is quite similar to other territorial pomacentrids (chiefly tropical) for which information exists.     

Predation risk assessment by green frog (<Emphasis Type="Italic">Rana clamitans</Emphasis>) tadpoles through chemical cues produced by multiple prey

Many prey assess predation risk through predator chemical cues. Numerous studies have shown that (1) prey sometimes respond to chemical cues produced by heterospecifics and (2) that many species are capable of associative learning. This study extends this research by focusing on predation risk assessment and antipredator behavior in environments containing chemical cues produced by multiple prey species. The results show that green frog (Rana clamitans) tadpoles (1) assess risk from the chemical cue produced during predation by a heterospecific (gray tree frog, Hyla versicolor, tadpoles) and (2) can exhibit similarly strong behavioral responses to a mix of conspecific and heterospecific cues compared to conspecific cue alone, depending on their conditioning environment. I then discuss how the prey choice of the predators and the relative abundances of the prey species should influence the informational value of heterospecific cues.     

Adult female hamsters avoid interspecific mating after exposure to heterospecific males

When females mate with a heterospecific male, they do not usually produce viable offspring. Thus, there is a selective pressure for females to avoid interspecific mating. In many species, females innately avoid heterospecific males; females can also imprint on their parents to avoid later sexual interactions with heterospecific males. However, it was previously unknown whether adult females can learn to discriminate against heterospecific males. We tested the hypothesis that adult females previously unable to avoid interspecific mating learn to avoid such mating after being exposed to heterospecific males. Syrian hamster (Mesocricetus auratus) females not previously exposed to Turkish hamster (Mesocricetus brandti) males can discriminate between odors of conspecific and heterospecific males, but they mate with either type of male. However, when we exposed adult females to both a conspecific male and a heterospecific male through wire-mesh barriers for 8 days, and then paired them sequentially with the two males, females were more receptive to conspecific males and more aggressive to heterospecific males. When females were paired with the heterospecific male first and the conspecific male second, no female was receptive and all were aggressive to heterospecific males. When females were paired with the conspecific male first, only 43% of females were then aggressive toward the heterospecific male. That is, interactions with conspecific males may decrease a female’s ability to properly avoid heterospecific males. Our study clearly shows for the first time that females can learn during adulthood to avoid interspecific mating just by being exposed to stimuli from heterospecific males.     

Experimental evidence that bright coloration is not important for territory defense in purple martins

Summary I tested the hypothesis that bright breeding plumage in territorial males acts as a badge of fighting ability or aggressive motivation to intimidate intruders. Territorial male purple martins (Progne subis) whose iridescent blue plumage was lightened to mimic the appearance of subadult males did not suffer an increase in intruder pressure or loss of territory compared with control males. Bright plumage color itself did not deter intruders and was not important for successful territory defense. Furthermore, a bright coloration of owners was not associated with an increased level of aggression toward intruders. Results from parallel studies on this species suggest that bright coloration is important in territory acquisition. The effectiveness of badges of fighting ability and aggressive motivation in territory defense is limited by whether intruders benefit from assessing these traits in owners. Differences in signaling systems between species are due in part to differences in floater tactics and the mode of territory acquisition.     

Differentiated phenotypic plasticity in larvae of the cannibalistic salamander Hynobius retardatus

Alternative phenotypes in natural populations can arise from either genetic polymorphism or an environmentally induced phenotype, that is, polyphenism. Evolutionary models of polyphenism developed by theoretical studies predict that polyphenism is favored when there are environment-dependent fitness trade-offs between alternatives and that the threshold frequency for a facultative switch between alternative phenotypes is adjusted in accordance with different selection regimes. The broad-headed (alternative) larval morph of Hynobius retardatus, which is induced by crowding with conspecifics or heterospecific anuran (Rana pirica) larvae, is a representative example of cannibalistic polyphenism. Morph induction by such proximate factors must reflect evolutionary (conditional frequency-dependent) processes. To clarify the role of frequency-dependent processes in polyphenism, I investigated the occurrence rate of the broad-headed morph under experimental crowding conditions (low conspecific, high conspecific, and high heterospecific densities) using larvae from eight natural populations with different larval densities of conspecifics and heterospecifics, and found interpopulational differences in the expression of the morph. Thus, there is a larval density-dependent equilibrium frequency of the morph in each pond, suggesting that the local switch point for morph induction was modified by selection to produce evolved differences between ponds. The evolution of such interpond differences has three necessary conditions: (1) There are pond-dependent fitness trade-offs between alternatives, (2) The maintenance of the morph is costly, and (3) The presence of conspecific or, especially, heterospecific larvae provides a reliable cue to the receiver.     

Host plant density and territorial behavior of the seed bug,Neacoryphus bicrucis (Hemiptera: Lygaeidae)

Summary Adults of the seed bug, Neacoryphus bicrucis, are most numerous in large host plant patches and where host plants are most dense within patches. Males patrol small territories composed of host plants and expel other males and unreceptive females. Larger males aggressively exclude smaller males from high quality territories where both host plants and females are most dense. Consequently, large males mate more frequently than small males. Males remain for longer time in areas where host plants are more dense. However, mating experience influences tenure within a host plant patch such that males tend to remain where they have recently mated. Courtship is aggressive and male territorial behavior is similar to courtship behavior. Preference for territories in areas of high host plant density appears to have been selected to increase the rate of encounter with females which preferentially oviposit in areas of high host plant density.     

Body morphologies shape territorial dominance in the satyrine butterfly <Emphasis Type="Italic">Lethe diana</Emphasis>

Male butterflies compete over mating territories via aerial interactions. It has often been suggested that flight performance, and thus flight-related traits, would play an important role in butterflies’ contest resolution; however, most studies have not demonstrated a clear relationship between these traits and territory ownership in butterflies. Males of the satyrine butterfly Lethe diana compete over territories via linear chases, a behavior that is uncommon among butterflies: rather, contests of most butterfly species consist of circling flights. In the present study, some morphological and physiological traits of L. diana were compared between territory owners and intruders to search for traits correlated with resource holding power (RHP). Territory owners had higher flight-muscle ratio (FMR) and were heavier than intruders, indicating that flight performance plays a key role in their contest resolution. Contest duration was not affected by the owners’ FMR or body mass, and thus I obtained no evidence supporting the hypothesis that contestants assess their relative RHP before making a decision to retreat. I speculate that the fact that these traits had an effect on territorial status in L. diana was a result of the characteristics of the contest behavior of this butterfly. During their contests, males L. diana fly faster in their linear flights than males of most other butterflies, which engage in slower circling flights. Therefore, males of L. diana probably need higher flight performance capabilities in order to win their contests.     

Heterospecific song matching in two closely related songbirds (Parus major and P. caeruleus): great tits match blue tits but not vice versa

To date, song research has focused primarily on the interactions of conspecifics. However, frequent interactions of songbirds with heterospecifics may necessitate adequate communication outside the species boundary. In this study, we focus on heterospecific communication behaviour of two small sympatric congeneric passerines, great and blue tits (Parus major and Parus caeruleus), which breed in overlapping territories and compete for food and nesting cavities. By means of a first playback experiment, we show that (1) heterospecific matching (imitating songs of the other species) is a strategy frequently used by great tits but not by blue tits, (2) both blue tit trilled and untrilled song can be accurately matched by great tits and that (3) almost half of the great tits in our study population match at least one blue tit song across all studied breeding stages, indicating that this heterospecific matching behaviour is a common feature in this population. A second playback experiment showed that these great tit imitations of blue tit songs do not function in intraspecific communication between male great tits. Hence, these heterospecific imitations appear to be designed for interspecific communication with blue tits. These findings suggest a strong heterospecific influence on the vocal learning process, repertoire composition and repertoire use in great tits and provide a possible mechanism that can drive song convergence in songbirds.     

An experimental study of song type function in the bobolink (Dolichonyx oryzivorus)

Summary We tested the hypothesis that the alpha and beta songs of male bobolinks (Dolichonyx oryzivorus) have separate intrasexual and intersexual functions by presenting caged males and caged females on the territories of male bobolinks. Although all males in our study population share both alpha and beta songs, we found no evidence for a specialized intersexual function of alpha song or a specialized intrasexual function of beta song. Territorial males increased their singing rate of both alpha and beta songs during both the male presentations and the female presentations. The proportions of the two song types did not change between control and experimental periods for either male or female presentations. We found no evidence in support of specialized intrasexual and intersexual functions of note types. Only 10% of the vocalizations initiated by territorial males were complete alpha or beta songs, while 87% were song fragments, and the remaining 3 % were compound songs. We did find that territorial males responded to simulated male intruders by increasing the proportion of fragmented songs and decreasing the proportion of compound songs. Moreover, males included fewer notes per song initiated and sang a higher proportion of songs that included only introductory notes during male presentations. We conclude that the vocal response of territorial male bobolinks to conspecific male intruders is to sing short, simple sequences of either song type. We found no consistent changes in vocal behavior of territorial males in response to female presentations other than increases in song rates.     

Territory quality and territorial behavior in two sympatric species of hummingbirds

Summary Changes in territorial behavior of blackchinned hummingbirds (Archilochus alexandri) in response to experimental changes in territory quality were investigated using artificial feeders and simultaneous, pair-wise observations of owners. Some of the responses of A. alexandri were similar to those documented by a previous study of the Anna's hummingbird (Calypte anna): A. alexandri defending rich territories spent more time on their territories, encountered a greater percentage of intruders, and chased more intruders than did A. alexandri defending poor territories. In contrast to C. anna, A. alexandri supplemented chases with energetically inexpensive threat vocalizations more extensively when territory quality was increased. This difference may be related to A. alexandri's more tenuous control of rich territories. When both species were observed on very poor territories, A. alexandri chased a greater percentage of intruders, consumed a greater proportion of available food, and obtained a greater net energy gain from their territories. When observed simultaneously on territories with ad lib food, both species defended highly exclusive territories but A. alexandri suffered higher intrusion pressure and spent more time and energy in defense. These interspecific differences in territorial behavior may facilitate sympatric coexistence of the two species through aggressive partitioning of flower patches according to productivity: the greater payoff received by C. anna on rich territories and A. alexandri on poor territories should favor a corresponding monopolization of rich areas by C. anna and poor areas by A. alexandri.     

Discrimination between related and unrelated individuals in the Australian lizard Egernia striolata

We examined evidence for kin-related signal discrimination in the Australian scincid lizard Egernia striolata, using 41 juvenile lizards from 14 litters from a population in the Mount Lofty Ranges, South Australia. We characterised each juvenile at four polymorphic microsatellite DNA loci, determined genetic relatedness among pairs of juveniles, and assigned for each litter one other litter that was genetically closest and one other litter that was genetically most distant. Lizards responded significantly more strongly, with tongue flicks and time in contact, to skin secretion stimuli from more distant than genetically close, unfamiliar conspecific juveniles. When presented with an intruder, juvenile lizards basked for shorter periods when the intruder was more distantly related, and aggressive lizards directed more aggressive acts towards more distantly related than closely related conspecific intruders. We deduce from these results that there is kin recognition in juvenile E. striolata, and that they are able to discriminate related from unrelated individuals among unfamiliar conspecifics.