Gulper, ripper and scrapper: anatomy of the neck in three species of vultures

Abstract

The head−neck system of birds is a highly complex structure that performs a variety of demanding and competing tasks. Morphofunctional adaptations to feeding specializations have previously been identified in the head and neck, but performance is also influenced by other factors such as its phylogenetic history. In order to minimize the effects of this factor, we here analyzed the anatomy of three closely related vultures that distinctly differ in feeding strategy. Vultures, as obligate scavengers, have occupied a special ecological niche by exclusively feeding on carrion. However, competition among sympatric vultures led to ecological differences such as preference of certain types of food from a carcass. Via comparative dissections we systematically described the craniocervical anatomy in the Griffon vulture (Gyps fulvus), the Cinereous vulture (Aegypius monachus) and the Hooded vulture (Necrosyrtes monachus) that exploit the same food resources in different ways. Our results revealed differences in the number of cervical vertebrae, in the morphology of the atlas−axis complex as well as in the neck musculature despite overall similarities in the musculoskeletal system. Gulpers, rippers and scrappers adopt specific postures while feeding from a carcass, but the cervical vertebral column is indispensable to position the head during all kinds of behavior. The great range of demands may explain the conservation of the overall muscle topography of the neck across the studied taxa.

Identification and Control of a 3-X Cable-Driven Manipulator Inspired From the Bird’s Neck

“…T Z(α)Z(α) Tα using the relationship between motors and X-joints rotation angles given in Eq. (21). Neglecting friction and cable elasticity, a first dynamic model can be derived as follows [9]:…”

“…The tensegrity joints used in our neck model are anti-parallelogram joints inspired from the Snelson's X-shape mechanisms [20], referred to as X-joints in this paper. As compared with simple revolute joints, X-joints do not have a fixed rotation axis, a common feature in biological joints [21,9]. Moreover, they have a number of advantages such as larger rotation ranges [4] and larger variations of stiffness [22].…”

Evolutionary versatility of the avian neck

“…Such adaptations to enhance the force and torque generating capacity of retractors muscles are likely to be relatively redundant in insectivores and indeed may actually be disadvantageous to both rapid neck extension and, in some taxa, rapid flight [ 65 ]. Recent work has suggested variation exists in the neck musculature of vultures [ 17 ], and it would therefore be interesting to examine finer-scale adaptations in the cervical system within groups such as carnivores (e.g. to assess potential adaptive responses to different prey types and modes of carnivory, such as predation versus scavenging).…”

“…Avian vertebral morphologies [3][4][5][6][7][8][9][10] and overall neck length [11] also display a wide diversity of form. However, no previous body of work has quantitatively addressed the ecomorphological signal in this variation, despite the clear functional significance and variability of the avian neck [2,17,18].…”

Presumed killers? Vultures, stakeholders, misperceptions, and fake news

“…Unlike the grasping and piercing talons of hawks or eagles aim at catching prey, vultures feet and claws adapted to walk on the ground and hold the carrion while eating it. Moreover, they generally have bare skin in their heads and necks which help them to avoid feather contamination when blood and flesh build up when feeding and sticking their heads inside a carcass (Böhmer, Prevoteau, Duriez, & Abourachid, 2020; del Hoyo et al, 1994, see also the thermoregulatory function hypothesis in Ward, McCafferty, Houston, & Ruxton, 2008). Their physiological adaptations, such as a low stomach pH and stable intestinal microbiome, allow them to cope with potentially pathogenic microorganisms present in their diet of decomposing flesh (Beasley, Koltz, Lambert, Fierer, & Dunn, 2015; Plaza, Blanco, & Lambertucci, 2020).…”