Drones as a tool to study and monitor endangered Grey Crowned Cranes (Balearica regulorum): Behavioural responses and recommended guidelines.

Crane populations are declining worldwide, with anthropogenically exacerbated habitat loss emerging as the primary causal threat. The endangered Grey Crowned Crane (Balearica regulorum) is the least studied of the three crane species that reside in southern Africa. This data paucity hinders essential conservation planning and is primarily due to ineffective monitoring methods and this species' use of inaccessible habitats. In this study, we compared the behavioural responses of different Grey Crowned Crane social groupings to traditional on-foot monitoring methods and the pioneering use of drones. Grey Crowned Cranes demonstrated a lower tolerance for on-foot monitoring approaches, allowing closer monitoring proximity with drones (22.72 (95% confidence intervals - 13.75, 37.52) m) than on-foot methods (97.59 (86.13, 110.59) m) before displaying evasive behaviours. The behavioural response of flocks was minimal at flight heights above 50 m, whilst larger flocks were more likely to display evasive behaviours in response to monitoring by either method. Families displayed the least evasive behaviours to lower flights, whereas nesting birds were sensitive to the angles of drone approaches. Altogether, our findings confirm the usefulness of drones for monitoring wetland-nesting species and provide valuable species-specific guidelines for monitoring Grey Crowned Cranes. However, we caution future studies on wetland breeding birds to develop species-specific protocols before implementing drone methodologies.

Spinescence and Total Phenolic Content Do Not Influence Diet Preference of a Critically Endangered Megaherbivore, but the Mix of Compounds Does.

In contrast to understanding spinescence in savanna woody species, little is known about the functions of plant secondary metabolites (PSM). Negative effects of PSMs on individual animal performance potentially translate into negative effects on herbivore population growth. Hence, understanding PSM functions is important for the conservation of savanna megafauna. We tested the view that black rhinoceros (Diceros bicornis) diet preference is not affected by spinescence or total phenolic abundance. We hypothesized that the composition of phenolic mixtures, however, would affect preference. Furthermore, we tested our data from 71 woody species for a trade-off between structural and chemical defenses. Spinescence type, and spinescence generally, did not deter black rhino feeding. Using eco-metabolomic data, we found that total abundance of phenolics did not affect preference, but mixture composition did and that the probability of spinescence trading off against phenolics depended on the mixture. We note that our study was restricted to black rhino and that diet preferences of other mammal herbivores might be influenced by subtle differences in phenolic mixtures. However, our results did support a previous, more detailed study of phenolic profiles of six species showing the same patterns in relation to preference generalised across mammal herbivore species in savannas. Our results represent substantial advancement in the understanding of the roles of PSMs, especially flavonoid compounds, in the functioning of savanna ecosystems, and highlight the need to dig deeper into broad groups of traits such as spinescence or total phenolics to improve understanding of woody plant defenses in savannas.