The portrayal of animal interactions in nature documentaries by David Attenborough and Bernhard Grzimek

Millions of people across the world have been exposed to the wildlife documentaries of David Attenborough and Bernhard Grzimek, who have thus greatly influenced the public’s views on nature and biodiversity. We investigated the way organisms’ biology is portrayed in these documentaries, quantifying different types of animal interactions shown. We evaluated 1498 (Attenborough) and 391 (Grzimek) interactions within- and between-species from documentaries covering a wide range of environments and animal taxa, first aired between 1956 and 2019. We tested whether the relative frequencies of different interactions were influenced by temporal trends as well as by the presenters and their production teams who likely reflect the given Zeitgeist in the UK compared to the European mainland. For our categorisation of animal interactions, we contrasted interspecific versus intraspecific interactions and antagonistic versus cooperative behaviour. While Grzimek’s documentaries put a stronger emphasis on cooperation and Attenborough’s on antagonistic behaviour, the trends were not statistically significant. Furthermore, these patterns show no significant change over time, contrasting with the changing view among biologists that cooperation is more predominant than considered in the traditional understanding of nature as ‘red in tooth and claw’

Does personality affect premating isolation between locally-adapted populations?

Background: One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system. Results: We characterized focal females for their personality and found behavioral measures of ‘novel object exploration’, ‘boldness’ and ‘activity in an unknown area’ to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females’ strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small. Conclusions: Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively

DNA methylation patterns of behavior-related gene promoter regions dissect the gray wolf from domestic dog breeds

A growing body of evidence highlights the relationship between epigenetics, especially DNA methylation, and population divergence as well as speciation. However, little is known about how general the phenomenon of epigenetics-wise separation of different populations is, or whether population assignment is, possible based on solely epigenetic marks. In the present study, we compared DNA methylation profiles between four different canine populations: three domestic dog breeds and their ancestor the gray wolf. Altogether, 79 CpG sites constituting the 65 so-called CpG units located in the promoter regions of genes affecting behavioral and temperamental traits (COMT, HTR1A, MAOA, OXTR, SLC6A4, TPH1, WFS1)-regions putatively targeted during domestication and breed selection. Methylation status of buccal cells was assessed using EpiTYPER technology. Significant inter-population methylation differences were found in 52.3% of all CpG units investigated. DNA methylation profile-based hierarchical cluster analysis indicated an unambiguous segregation of wolf from domestic dog. In addition, one of the three dog breeds (Golden Retriever) investigated also formed a separate, autonomous group. The findings support that population segregation is interrelated with shifts in DNA methylation patterns, at least in putative selection target regions, and also imply that epigenetic profiles could provide a sufficient basis for population assignment of individuals

Different preference functions act in unison: mate choice and risk-taking behaviour in the Atlantic molly (Poecilia mexicana)

Consistent individual differences in behaviour (animal personality) are widespread throughout the Animal Kingdom. This includes variation in risk-taking versus risk-averse behavioural tendencies. Variation in several personality dimensions is associated with distinct fitness consequences and thus, may become a target of natural and/or sexual selection. However, the link between animal personality and mate choice—as a major component of sexual selection—remains understudied. We asked (1) whether females and males of the livebearing fish Poecilia mexicana prefer risk-taking mating partners (directional mating preference), (2) or if their preferences are dependent on the choosing individual’s own personality type (assortative mating). We characterized each test subject for its risk-taking behaviour, assessed as the time to emerge from shelter and enter an unknown area. In dichotomous association preference tests, we offered two potential mating partners that differed in risk-taking behaviour but were matched for other phenotypic traits (body size, shape, and colouration). Females, but not males, exhibited a strong directional preference for risk-taking over risk-averse mating partners. At the same time, the strength of females’ preferences correlated positively with their own risk-taking scores. Our study is the first to demonstrate that a strong overall preference for risk-taking mating partners does not preclude effects of choosing individuals’ own personality type on (subtle) individual variation in mating preferences. More generally, two different preferences functions appear to interact to determine the outcome of individual mate choice decisions

Context-dependent female mate choice maintains variation in male sexual activity

The existence of individual variation in males' motivation to mate remains a conundrum as directional selection should favour high mating frequencies. Balancing selection resulting from (context-dependent) female mate choice could contribute to the maintenance of this behavioural polymorphism. In dichotomous choice tests, mosquitofish (Gambusia holbrooki) females preferred virtual males showing intermediate mating frequencies, reflecting females' tendencies to avoid harassment by highly sexually active males. When tested in the presence of a female shoal—which protects females from male harassment—focal females showed significantly stronger preferences for high sexual activity. A trade-off between (indirect) benefits and (direct) costs of mating with sexually active males probably explains context-dependent female mate choice, as costs depend on the social environment in which females choose their mates. No preference was observed when we tested virgin females, suggesting that the behavioural pattern described here is part of the learned behavioural repertoire of G. holbrooki females

Does the presence of conspecifics facilitate exploratory behaviour in a cichlid fish (Etroplus suratensis)?

Animals confronted with any kind of novelty show behavioural responses driven by avoidance and exploration. The expression of both tendencies is modulated by anxiety. Especially in group -living animals, the presence of conspecifics can reduce anxiety in novel situations and hence increase exploratory tendency. Such intensified behavioural responses triggered by the social envi-ronment of an individual are called social facilitation. Here, we tested for social facilitation on the exploratory tendency of group-living juvenile Green chromide cichlid fish (Etroplus suratensis) by assessing each individual twice in an open field test: once alone and once together with a conspe-cific. Contrary to our expectations, we found no difference in exploratory behaviour between the groups. However, our results suggest that changes in exploratory tendency across the two treat-ments were highly individual, both in extent and direction, and are likely driven by the presence of the conspecific and the focal individual's own behavioural type

Natural variation in social conditions affects male mate choosiness in the amphipod Gammarus roeselii

The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition, quality assessment and opportunity costs. Our knowledge about natural variation in male mate choosiness across different populations of the same species, however, remains limited. In this study, we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii (Gervais 1835), a species with overall high male mating investments, and evaluated the relative influence of population density and sex ratio (both affecting mate availability) on male mate choosiness. We investigated amplexus establishment after separating mating pairs and presenting focal males with a novel, size-matched female from the same population. Our analysis revealed considerable effects of sex ratio and (to a lesser extent) population density on time until amplexus establishment (choosiness). Male amphipods are able to perceive variable social conditions (e.g., sex ratio) and modify their mating strategy accordingly: We found choosiness to be reduced in increasingly male-biased populations, whereas selectivity increases when sex ratio becomes female biased. With this, our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio (i.e., level of competition) for male mating decisions in natural environments. Accounting for variation in sex ratios, therefore, allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies

Additional file 4 of The portrayal of animal interactions in nature documentaries by David Attenborough and Bernhard Grzimek

Additional file 4. Spreadsheet with summary of movie, name, interaction, presenter, and time in documentaries by Attenborough and Grzimek

Additional file 3 of The portrayal of animal interactions in nature documentaries by David Attenborough and Bernhard Grzimek

Additional file 3. Statistical analyses in R environment

Additional file 2 of The portrayal of animal interactions in nature documentaries by David Attenborough and Bernhard Grzimek

Additional file 2. Summary graph of the interactions in documentaries by Attenborough and Grzime