Cultural transmission, the social learning of information or behaviors from conspecifics 1–5, is believed to occur in a number of groups of animals, including primates 1, 6–9, cetaceans 4, 10, 11, ...and birds 3, 12, 13. Cultural traits can be passed vertically (from parents to offspring), obliquely (from the previous generation via a nonparent model to younger individuals), or horizontally (between unrelated individuals from similar age classes or within generations) 4. Male humpback whales (Megaptera novaeangliae) have a highly stereotyped, repetitive, and progressively evolving vocal sexual display or “song” 14–17 that functions in sexual selection (through mate attraction and/or male social sorting) 18–20. All males within a population conform to the current version of the display (song type), and similarities may exist among the songs of populations within an ocean basin 16, 17, 21. Here we present a striking pattern of horizontal transmission: multiple song types spread rapidly and repeatedly in a unidirectional manner, like cultural ripples, eastward through the populations in the western and central South Pacific over an 11-year period. This is the first documentation of a repeated, dynamic cultural change occurring across multiple populations at such a large geographic scale.
► Humpback whale songs have repeatedly moved east across the South Pacific ► The songs moved across the region in a series of cultural waves ► The waves frequently caused complete “cultural revolution” of the song ► The scale, rate, and repetition of these cultural changes are unparalleled
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Cleaning behaviour is deemed a mutualism, however the benefit of cleaning interactions to client individuals is unknown. Furthermore, mechanisms that may shift fish community structure in the ...presence of cleaning organisms are unclear. Here we show that on patch reefs (61-285 m²) which had all cleaner wrasse Labroides dimidiatus (Labridae) experimentally removed (1-5 adults reef⁻¹) and which were then maintained cleaner-fish free over 8.5 years, individuals of two site-attached (resident) client damselfishes (Pomacentridae) were smaller compared to those on control reefs. Furthermore, resident fishes were 37% less abundant and 23% less species rich per reef, compared to control reefs. Such changes in site-attached fish may reflect lower fish growth rates and/or survivorship. Additionally, juveniles of visitors (fish likely to move between reefs) were 65% less abundant on removal reefs suggesting cleaners may also affect recruitment. This may, in part, explain the 23% lower abundance and 33% lower species richness of visitor fishes, and 66% lower abundance of visitor herbivores (Acanthuridae) on removal reefs that we also observed. This is the first study to demonstrate a benefit of cleaning behaviour to client individuals, in the form of increased size, and to elucidate potential mechanisms leading to community-wide effects on the fish population. Many of the fish groups affected may also indirectly affect other reef organisms, thus further impacting the reef community. The large-scale effect of the presence of the relatively small and uncommon fish, Labroides dimidiadus, on other fishes is unparalleled on coral reefs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Introduced predators such as feral cats (Felis catus) are responsible for declines of many small mammals across the globe. The impact of cats can be exacerbated by mesopredator release, when larger ...predators (e.g. canids) are suppressed. In response to increasing predation threat from cats, native species may change their use of landscapes. We studied how interactions among native and introduced predators affect the decline of the largest native predator in northern Australia, the endangered northern quoll (Dasyurus hallucatus). The northern quoll is a carnivorous marsupial 'that is undergoing rapid population declines in most of its range, and is retreating to rugged, rocky parts of the landscape. Widespread dingo (Canis dingo) control has been hypothesized to lead to mesopredator release of cats in parts of the continent. Using camera trapping and GIS mapping methods, we determined the temporal activity and spatial distributions of sympatric northern quolls, dingoes and cats in the semi-arid Pilbara region of Western Australia. We found that dingoes were scarce, and their role as top predators in our study areas was weak. Cats avoided dingoes in time at a fine scale, but their spatial distribution was not affected by dingoes. Cats frequently used flat, open habitats. Quolls avoided areas used by cats. We suggest that introduced predators influence the use of landscapes by northern quolls at both local and larger scales. Predator avoidance is likely to be a major reason for the contraction of the distribution of northern quolls to rocky areas across northern Australia.
•Dingoes did not co-occur with northern quolls.•Ecological absence of dingoes has allowed mesopredator release of cats.•Northern quolls and cats use different habitats.•Cats may have pushed northern quolls out of grasslands, into rocky habitats.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Group size is known to affect both the amount of time that prey animals spend in vigilance and the degree to which the vigilance of group members is synchronized. However, the variation in group-size ...effects reported in the literature is not yet understood. Prey animals exhibit vigilance both to protect themselves against predators and to monitor other group members, and both forms of vigilance presumably influence group-size effects on vigilance. However, our understanding of the patterns of individual investment underlying the time sharing between anti-predator and social vigilance is still limited. We studied patterns of variation in individual vigilance and the synchronization of vigilance with group size in a wild population of eastern grey kangaroos (Macropus giganteus) subject to predation, in particular focusing on peripheral females because we expected that they would exhibit both social and anti-predator vigilance. There was no global effect of group size on individual vigilance. The lack of group-size effect was the result of two compensating effects. The proportion of time individuals spent looking at other group members increased, whereas the proportion of time they spent scanning the environment decreased with group size; as a result, overall vigilance levels did not change with group size. Moreover, a degree of synchrony of vigilance occurred within groups and that degree increased with the proportion of vigilance time peripheral females spent in anti-predator vigilance. Our results highlight the crucial roles of both social and anti-predator components of vigilance in the understanding of the relationship between group size and vigilance, as well as in the synchronization of vigilance among group members.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Many studies of animal personality are completed in the laboratory with animals collected from the wild. However, there is some concern that studies that trap individuals to perform assessments of ...personality may not collect a representative sample of personality types, as some individuals may be trap-shy. We investigated the relationship between boldness and trappability using males of a species of lizard, the Namibian rock agama, Agama planiceps, whose boldness could be assessed in the wild prior to trapping. We observed known individuals between nine and 15 times each over several weeks, which revealed that boldness consistently differed across individuals and was not influenced by factors such as body size or environmental variables. Lizards habituated to the behavioural assay, but there was no evidence of plasticity (individual differences) in the rate of habituation. As predicted, bold individuals entered the trap sooner than shy individuals and we had higher success at trapping bold individuals. Using a simple simulation model, we show that such bias leads to underestimates of effect size and reduces the power to detect correlations between behavioural traits (i.e. behavioural syndromes). We suggest that studies that trap animals for laboratory assessments of personality may consistently underrepresent the extent of personality trait variation in the populations that they sample, and recommend that future studies either develop methods for testing personality in the field that control for obvious confounding variables or make every effort to ensure minimum bias when sampling animals for use in a laboratory setting.
► We investigated the relationship between boldness and trappability using male lizards. ► Bold individuals were easier to trap than shy individuals. ► We use a simulation model to investigate the effect of trappability bias. ► We show that trappability bias underestimates correlations between behavioural traits.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Long-term studies of sociality in wild animals are rare, despite being critical for determining the benefits of social relationships and testing how long such relationships last and whether they ...change as individuals age. Knowledge about social relationships in animal species that exhibit fission–fusion dynamics can enhance our understanding of the evolution of close social bonds in humans, who also have a fission–fusion social system. We analysed the social network of wild giraffes, Giraffa camelopardalis, in Etosha National Park, Namibia, from 1102 records of group compositions, including 625 individually identified individuals, spanning 6 years. We found that giraffes, which exhibit fission–fusion sociality, formed a cohesive society with short path lengths across the network that may facilitate passive information sharing about resource availability. Male and female giraffes appeared to contribute equally to the network structure, based on similarities between the sexes for five network metrics. However, using lagged association rates, we found that long-term relationships spanning 6 years were evident among female giraffes, but not males, which may be explained by sex differences in ranging patterns and reproductive priorities. Five network metrics of females were compared between two adult age cohorts to investigate whether females' ages influenced sociability. As younger females reached adulthood, they associated with greater numbers of females and increased their network strength and social connectivity, perhaps because of dispersal. Our study reinforces the value of network analysis and long-term studies for examining the social systems of wild animals.
•The giraffes' social network and patterns of association were stable over time.•The mean path length between any two giraffes was less than two.•Both sexes contributed equally to the network structure.•Long-term relationships spanning 6 years occurred among females but not males.•Female giraffes increased their sociability upon reaching adulthood.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Many species exhibit fission–fusion dynamics, yet the factors that influence the frequent changes in group size and membership in these species have not been widely studied. Social ties may be ...influenced by kinship but animals may also form preferred associations because of social attraction or may only associate because they have similar habitat preferences. We investigated the association patterns of 535 wild giraffes, Giraffa camelopardalis, in Etosha National Park, Namibia using behavioural and genetic data from individually identified giraffes. We collected 726 records of group composition over a 14-month period and calculated pairwise association indices, which were tested against a null model. We found that female–female pairs, but not male–male pairs, showed both preferred and avoided relationships. We tested whether females' relationships could be explained by the degree of relatedness between pairs and whether pairs overlapped spatially. Correlations between matrices of pairwise associations, spatial overlap and relatedness showed that female–female associations were strongly correlated with amounts of spatial overlap and pairs that exhibited preferred relationships were more closely related than would be expected by chance. However, only about one-quarter of the variation in observed associations could be explained by spatial overlap and relatedness and therefore much of this variation may have been related to individual social preferences.
► We found sex differences in giraffe sociality. ► Female giraffes showed nonrandom association patterns. ► Female giraffes showed preferred and avoided relationships with other females. ► Spatial overlap or kinship did not entirely explain female–female relationships. ► Female individual preferences may contribute to variation in female sociality.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Male humpback whales produce complex songs during the breeding season, yet the singing behaviour of males and whether songs function in male contests and/or through female choice are still poorly ...understood. We investigated song function by obtaining simultaneous observations of the positions and movements of singing and nonsinging whales in real time during their migration off the east coast of Australia. We collected movement data by acoustic tracking using a hydrophone array, land-based visual tracking and observations from a small boat. Of the 114 singers analysed, 66 (58%) associated with conspecifics. Singers were significantly more likely to join groups containing a mother–calf pair than other groups. Males started to sing after joining groups only if they consisted of a mother–calf pair not escorted by another male. Singers also associated longer and sang for a significantly greater proportion of time with mother–calf pairs than any other group type. Associating with mother–calf pairs has been shown to be a reproductively successful strategy for males. In contrast, whales that joined singers were usually lone males; these associations were brief and singers typically stopped singing in the presence of other males. This is the highest reported incidence in humpback whales of males singing when escorting females and supports an intersexual function of song in humpback whales. We suggest that males joining singers are prospecting for females rather than engaging in male social ordering and that singing may incur the cost of attracting competing males.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Prey animals often have to trade off foraging against vigilance. However, vigilance is costly and individuals are expected to adjust their vigilance and its cost in relation to social cues and their ...predation risk. To test this, we conducted playback experiments in the field to study how lions' (Panthera leo) roars and male impalas' (Aepyceros melampus) territorial vocalizations affected the vigilance and foraging behaviours as well as movements of female impalas. Our results show that impalas adjusted their activities in different ways depending on the vocalizations broadcast. After lions' roars were played, female impalas increased their vigilance activity (in particular increasing their high-cost vigilance--vigilance without chewing), decreased their bite rates and increased their movements, whereas male impalas' vocalizations caused females to decrease their vigilance (decreasing their low-cost vigilance--vigilance while chewing) and increase their movements without affecting their bite rates. Therefore, it appears that predators' vocalizations stimulate anti-predator behaviours such as vigilance and movement at the expense of foraging, whereas males' vocalizations increase individuals' displacements at the expense of vigilance. Overall, this study shows that both predator and social cues have direct effects on the behaviour of gregarious prey and need to be considered in future studies.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Theory suggests that the distributions of threatened species do not generally contract to the species' core habitat. Rather, surviving populations that decline to range edges often persist in ...suboptimal habitat because it is least affected by their important threats. The northern quoll (Dasyurus hallucatus) is an endangered carnivorous marsupial that occurs in patchy populations across northern Australia, now almost entirely in rugged habitats. The overall goal of this study was to assess differences in quality across available habitat types to determine if rugged habitats do constitute higher quality habitat for northern quolls, as no field data are yet available to test this hypothesis. Through fieldwork in the Pilbara (Western Australia), we assessed habitats based on vegetation, shelter availability, and prey availability. While we did not find significant differences in prey availability across habitats, we found differences in the availability of potential dens and temporary shelters suggesting that shelters are of higher abundance in rocky‐riparian and rocky habitats. Habitat associations of prey suggest that northern quolls in rocky‐riparian habitats may feed or subsidize their diets with prey from adjacent habitats including grasslands, which carry risk of predation by feral cats in our study area. Our results agree with GIS‐based studies from the Pilbara, namely rugged habitats currently represent the highest quality habitat for northern quolls there. There are two nonexclusive hypotheses explaining the contraction of quolls to rocky habitats; we found stronger support for the den hypothesis than the prey availability hypothesis, suggesting that shelter availability is an important current determinant of habitat quality for northern quolls in the Pilbara. Our study helps to highlight the role of den availability and temporary cover as a crucial component of habitat quality for northern quoll presence and abundance across the landscape under current conditions.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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