In this research update we summarize articles about research that investigates why Bearded Vultures colour their plumage with reddish soil; a commentary about how to improve livestock carcass monitoring to inform policy and regulations with implications for human sanitation and health; and an assessment of whether behaviour changes or biased perceptions drive reports of negative vulture-livestock interactions.
• This article investigates the reason why Bearded Vultures often visit springs and water sources containing iron oxides (ferruginous) to bathe in mud to add a reddish colour to their plumage.
• Three hypotheses have been proposed to explain the deliberate colouration of plumage by Bearded Vultures:
i. To signal individual dominance status
ii. Iron oxides might have anti-bacterial and anti-parasitic properties which reduce feather degradation and produce other benefits
iii. Incubating Bearded Vultures might transfer this protection to their developing embryos and increase hatching success
• The researchers investigated the antibacterial hypothesis by applying feather-degrading bacteria to coloured and uncoloured feathers; assessing the anti-bacterial activity of ochre (earth rich in iron oxide); and comparing the breeding success of individuals which coloured their plumage to those that did not and remained pale.
• Key results:
i. Colouring feathers with ochre did not delay feather degradation
ii. Iron particles from ochre soil or iron salts had no antibacterial effect
iii. Breeding success did not differ between territories occupied by pale individuals compared to individuals that coloured their plumage
• The authors conclude that plumage colouring by Bearded Vultures is unlikely to have an antibacterial role but that the primary function is to signal territorial status and may also be involved in other processes such as pair formation and maintaining pair bonds, as suggested for Egyptian Vultures which also colour their plumage (Van Overveld, de la Riva & Donázar (2017)).
• The authors of this commentary article discuss some of the challenges and opportunities of integrating conservation issues into laws and policies concerning human sanitation and health, with a focus on the ecosystem services provided by vultures and other scavengers of livestock carrion.
• After the outbreak of Bovine Spongiform Encephalopathy (BSE) in the late 1980s, EU sanitary regulations prohibited the abandonment of livestock carcasses in the field to prevent potential risks for animal health that could in turn compromise public health. This resulted in sudden food shortages for vultures and other scavengers, the consequences of which are also discussed in the next reviewed article.
• The article describes how, in some regions and countries, the regulations were modified to allow the abandonment of carcasses in defined scavenger feeding zones (SFZs), but several implementation gaps limit the effectiveness of the modified regulations.
• For example, the criteria for designating SFZs depends upon accurate calculation of scavenger feeding requirements (SFRs) which can be very variable due to uncertainty about key elements of scavenger ecology (e.g. accurate estimates of population size and individual metabolic needs). The authors state that, “clear criteria on how to estimate SFRs are lacking across European and domestic laws.”
• The authors recommend that policymakers establish systematic livestock carcass monitoring to detect implementation gaps (e.g. food shortages that might impact scavenger populations; implications for disease transmission), and to modify EU sanitary regulations accordingly. This monitoring would enhance cross-compliance with regulations, improve disease surveillance and simultaneously increase knowledge about scavenger ecology, and potentially set an example of best practice at a global scale.
Come to the European Vulture Conference this October to hear more about this and other topics from the lead author, Dr Patricia Mateo-Tomás, who will be giving a keynote presentation.
Figure 1. Bias and uncertainty in estimating scavenger feeding requirements (SFRs).
Estimated SFRs (mean: black dot ± minimum-maximum range: error bars in tons/year on the x-axis) for the Spanish populations of an obligate (griffon vulture Gyps fulvus) and two facultative (brown bear Ursus arctos and wolf Canis lupus) vertebrate scavengers targeted by
European sanitary regulations. Calculations of SFRs from simple (i.e. “Daily food intake
(DFI)”, the quantity of food that an individual should ingest per day to keep its basic metabolic functions; see Mateo-Tomás et al. 2017) to more complex (i.e. “% carrion in diet”) scenarios (on the x-axis) result from progressively incorporating various parameters into
Equation (1) (see details in Appendix S2). The progressive incorporation of more information on the species demography and feeding ecology is expected to improve the ecological soundness (i.e. reducing bias) of the SFRs estimates (black dot), but it would also increase total uncertainty (shaded background) around such estimates due to the accumulation of the inherent uncertainty of the new incorporated parameters (light-coloured background). Zoomed data are provided, on the left axis, for bear and wolf populations to show the increase of uncertainty in the estimates better. Note that SFRs here provided are based on the best evidence available but are not exact figures; this is rather intended as a representation of the uncertainty in the estimates. (Source: Mateo-Tomas et al. (2019)
• The authors of this study, which include VCF advisory board members Olivier Duriez and Raphaël Néouze, investigate whether patterns of complaints of Griffon Vultures attacking livestock could be explained by changes in vulture behaviour, or by biased perceptions by farmers.
• In the Grands Causses region of southern France, there were 156 official reports about vultures attacking livestock over eight years (2007-2014). 56.4% of the reports concerned sheep (28.4% less than one year old) and 42.3% concerned cattle (68.2% less than one year old).
• The spatio-temporal distribution of complaints was not correlated with the vulture population trend and was not centred on the population core area, with 40% of the complainants’ farms located outside protected areas where most awareness and education programs take place. 90% of the complainants did not own or manage supplementary feeding stations for vultures.
• In 67% of the reports, vultures consumed livestock that had already died, while in 18% of cases vultures consumed livestock that was initially still alive but immobile and very close to death. Importantly, there were no witnesses in 95% of the incidents.
• The authors conclude that the evidence shows that perception bias due to lack of knowledge was most likely to explain this vulture-livestock conflict rather than any recent change in vulture behaviour that would indicate a shift in consuming dead animals to live animals.
• To reduce misinformed negative perceptions of vultures, the authors recommend extending education and awareness programmes to areas where vultures are recolonising their former range.
• At VCF, we have recently produced a poster that reviews some of the evidence about vulture-livestock incidents across Europe, and some recommended measures to mitigate the perceived problem.