Scouts vs Usurpers: Alternative foraging strategies facilitate
coexistence between Neotropical Cathartid Vultures
Abstract
1. Understanding how diverse assemblages of scavengers can coexist on
shared ecological resources is a fundamental challenge in community
ecology. However, current approaches typically focus on behaviour at
carcass provisioning sites, missing how important differences in
movement behaviour and foraging strategies can facilitate sympatric
species coexistence. Such information is particularly important for
vultures - obligate scavengers representing the most endangered avian
foraging guild. Their loss from ecosystems can trigger trophic cascades,
mesopredator release, and disease outbreaks. 2. We use a combination of
morphometric measurements and movement data from wild King (Sarcoramphus
papa) and Greater yellow-headed (Cathartes melambrotus) vultures,
coupled with carcass visitation data from animal carcass provisioning
experiments to characterise scavenger community structure and strategies
in the Peruvian Amazon. 3. King vulture body mass and tarsi length were
larger (43% and 45% respectively), and tail shorter (22%) than the
Greater-yellow headed vulture. King vultures also had substantially
larger home ranges (~500%), flew higher than Greater
yellow headed vultures (695m vs. 360 m), and despite flying similar
distances each day, were active later in the day. At carcasses,
Greater-yellow headed vultures typically arrived first, but were rapidly
outnumbered by both King and Black vultures (Coragyps atratus). 4. We
find that the movement behaviour of obligate apex scavengers in the
western Amazon is linked to their ability to coexist - the Greater
-yellow headed vultures, a smaller stature ‘scouting’ species adapted to
fly low and forage early, arrive first, but are ultimately displaced by
larger-bodied king vultures at large ephemeral carrion resources.
Expansion of future GPS tracking initiatives should facilitate the
exploration of direct facultative interactions from animal movement data
and give further insight into how diverse communities assemble and
interact.