First evidence of scavenging behaviour in the herbivorous lizard Uromastyx aegyptia microlepis

Abstract

In this study, we provide the first evidence of scavenging behaviour in the spiny-tailed agamid lizard (Uromastyx aegyptia microlepis), a species which heretofore has been considered a strict desert herbivore. We examined 294 faecal samples collected in the desert of Qatar and found that 84% of the faeces (n = 247) contained exclusively plant material. Grains of barley (Hordeum vulgare) were present, suggesting that Uromastyx can benefit from the food provided to livestock when wild plants are scarce. We also found remains of invertebrates, vertebrates and stones in the lizard faeces. The type of vertebrate remains found suggests scavenging behaviour and some flexibility in feeding behaviour where food resources are scarce. Overgrazing by camels and goats in the area may affect food availability for Uromastyx populations, suggesting the need for conservation measurements in the Qatar desert.

Introduction

Scavenging is a widespread phenomenon in vertebrate communities, and is usually viewed as a random and opportunistic behaviour that requires specific circumstances to occur (Cramer, 2008). Unfortunately, most studies on scavenger assemblages have presented an oversimplified view of carrion foraging (Selva and Fortuna, 2007). However, the high diversity of carrion resources and consumers, the differential predictability of the carcass types, and the stressful environmental conditions, contradict this conventional view (Selva and Fortuna, 2007). Scavenging is an important behavioural strategy used to overcome temporal fluctuations in food resources in species living in arid and harsh environments (Amor et al., 2010).

Optimal Foraging Theory predicts flexibility in feeding behaviour allowing species to survive in harsh environments where food resources may be scarce and unpredictable in space and time (Barrette et al., 2010). In dry and harsh environments some lizard species and populations cannibalize juveniles and eggs (Castilla and Van Damme, 1996), consume marine crustaceans (Castilla et al., 2008), or noxious prey (Castilla and Herrel, 2009), to obtain the food needed to meet their energetic requirements.

Lizards of the genus Uromastyx are considered to be specialized herbivores (Foley et al., 1992, Herrel and De Vree, 2009). However, few studies exist on the food and feeding habits of the spiny-tailed lizard (Uromastyx aegyptius microlepis) in the field except for few studies conducted in Arab countries (Kevork and Al-Uthman, 1972, Robinson, 1995, Cunningham, 2000) or under captive conditions (Dickson, 1965). Preliminary studies suggest that U. a. microlepis consumes insects, lizards and other food sources in both the field and laboratory (Kevork and Al-Uthman, 1972, Throckmorton, 1978, Robinson, 1995, Cunningham, 2000).

Considering these observations, it can be questioned whether all species of the genus Uromastyx, are entirely herbivorous. Given the harsh desert environment in which these animals live, plasticity in feeding behaviour depending on seasonal or geographical variation in food resources seems likely. In this study we explored the hypothesis that the herbivorous spiny-tailed lizard, U. a. microlepis, a species living in dry desert areas may behave as an omnivorous species under conditions of limited food availability. To do so, we examined the diet of this species based on faecal pellets collected in the desert of Qatar.