Relationships between male giraffes’ colour, age and sociability

In species in which males signal competitive ability through secondary sexual traits, males with different levels of trait expression may adopt different reproductive tactics to maximize their reproductive success. In fission–fusion social systems, the most dominant males often roam widely in search of females in oestrus, and thus exhibit different patterns of sociability from subordinate males that utilize alternative reproductive tactics. Giraffes, Giraffa camelopardalis, are rare among mammals in that they are sexually dimorphic in colour, and colour is hypothesized to function as a signal of males’ social status by displaying their competitive ability. Here we analysed the coat colour and sociability of 66 wild male giraffes over 12 years at Etosha National Park in Namibia to test two premises underlying this hypothesis. First, we found that males did not all darken at the same rate or to the same degree, and colour variation increased with age. This suggests that colour is not solely an age-based trait but could be a secondary sexual trait. We then showed a distinct difference in the sociability of both young and pale males compared to darker males. Both younger and paler old males tended to be more gregarious while darker males were more solitary. This is consistent with a system where darker, more dominant males roam looking for females in oestrus. Younger or subordinate males may delay roaming or use an alternative tactic, such as remaining in groups with females to gain copulations when a more dominant male is not present. Our results are consistent with the hypothesis that male giraffe coat colour functions as a signal of social status through competitive ability, but deeper study into movement patterns and the costs and benefits associated with darker colours is required

Butterflies on the brink: identifying the Australian butterflies (Lepidoptera) most at risk of extinction

The diversity and abundance of native invertebrates is declining globally, which could have significant consequences for ecosystem functioning. Declines are likely to be at least as severe as those observed for vertebrates, although often are difficult to quantify due to a lack of historic baseline data and limited monitoring effort. The Lepidoptera are well studied in Australia compared with other invertebrates, so we know that some species are imperilled or declining. Despite this, few butterfly taxa are explicitly listed for protection by legislation. Here we aim to identify the butterfly taxa that would most benefit from listing by determining the Australian butterflies at most immediate risk of extinction. We also identify the research and management actions needed to retain them. For 26 taxa identified by experts and various conservation schedules, we used structured expert elicitation to estimate the probability of extinction within 20 years (i.e. by 2040) and to identify key threatening processes, priority research and management needs. Collation and analysis of expert opinion indicated that one taxon, the laced fritillary (Argynnis hyperbius inconstans), is particularly imperilled, and that four taxa (Jalmenus eubulus, Jalmenus aridus, Hypochrysops piceatus and Oreisplanus munionga larana) have a moderate–high (>30%) risk of extinction by 2040. Mapped distributions of the 26 butterflies revealed that most are endemic to a single state or territory, and that many occupy narrow ranges. Inappropriate fire regimes, habitat loss and fragmentation (through agricultural practices), invasive species (mostly through habitat degradation caused by weeds and rabbits) and climate change were the most prevalent threats affecting the taxa considered. Increased resourcing and management intervention will be required to prevent these extinctions. We provide specific recommendations for averting such losses