Supplement: coprophagy in leporids and other mammalian herbivores

In reviewing coprophagy (more precisely, reingestion: ingesting own faeces directly from the anus) in mammalian herbivores (Hirakawa, 2001), I stated that the Capybara (Hydrochaerus hydrochaeris) does not have a colonic separation mechanism, nor does it practise reingestion, following Hörnicke & Björnhag (1980). After publishing this article, Professor Ian Hume in Australia informed me that the Capybara has a selective retention (i.e. separation) mechanism, does practise coprophagy and introduced me to an article (Borges, Dominguez-Bello & Herrera, 1996) that I had overlooked. I then found two other articles that described coprophagy in the Capybara (Herrera, 1985; Mendes et al., 2000). In this supplement, I briefly describe the reingestion pattern in the Capybara and revise my previous overview of coprophagy in mammalian herbivores. The Capybara’s daily rhythm of reingestion in the wild (Herrera, 1985) is very similar to that in leporids. The Capybara typically rests in the morning, grazes in the late afternoon and evening, and spends nights alternately grazing and resting. Reingestion is practised during daytime resting periods (07:00–14:00), while most faeces are voided during grazing at night (Ojasti, 1973). Although Herrera’s nocturnal observations were not continuous, the observations by Mendes et al. (2000) on Capybaras in captivity confirm that reingestion does not occur during the night. The described sequence of reingestion behaviour in the Capybara (Herrera, 1985) is also similar to that in leporids and other reingesting herbivores. The reingested ‘pasty’ faeces are richer in protein and poorer in gross fibre than the voided ‘ovalshaped’ faeces (Mendes et al., 2000). The description indicates that the two types of faeces are both nutritionally and morphologically differentiated, hence they are what I have referred to as soft and hard faeces in my review. It also suggests that the soft faeces (caecotroph) are an amorphous type, not a ‘capsule’ type covered with a tough membrane (Hirakawa, 2001). Whether the Capybara also reingests hard faeces is not known. Borges et al. (1996) stated that the nitrogen and neutral detergent fibre (NDF) contents in the caecum, colon and stomach of the Capybara dynamically change over a day, suggesting the existence of a separation mechanism. Overall, the daily reingestion rhythm and digestion style in the Capybara are amazingly similar to those observed in leporids, the Coypu (Myocastor coypus) and the Ringtail Possum (Pseudocheirus peregrinus). Accordingly, the Capybara should be grouped together with them in fig. 5 in Hirakawa (2001). Figure 6 in Hirakawa (2001) should also be revised as shown in Fig. 1 here. The Capybara is certainly the largest mammalian herbivore to practise reingestion. Professor Hume (personal communication) further suggested that the Common Mammal Rev. 2002, Volume 32, No. 2, 150–152. Printed in Great Britain.