Petauroides volans is a highly specialized folivore, who feeds about 90% of its diet on eucalyptus leaves. It relies on high nutrient species or growth stages, and seems to be able to actively select these high-quality leaves based on tree species and leaf age. All the remaining species, so-called ringtails, also are folivores, and at least some species, such as Pseudocheirus peregrinus, are also capable of eating high amounts of eucalyptus leaves. However, they mostly do not rely so heavily on eucalypts alone, eating buds, flowers and fruits of other plants, in the understory of eucalypt forests as well. All leaf-eating pseudocheirids are hindgut-fermenters, which means that in their large colon and cecum, a specialized community of bacteria and other microorganisms is kept to digest cellulose (plant cell walls cannot be digested by any animal). They are all capable, in their hindgut, to separate the contents into large particles, which are defecated rather quickly, and small particles, solubles and bacteria themselves. This mechanism serves to retain the more digestible parts and nitrogen-carrying bacteria. Ringtail possums also are caecotrophic; the colon contents are defecated separately, and ingested again to gain proteins and amino acids by foregut digestion. Eucalypt-feed-ing ringtails often show strong preferences for certain trees, and dislike for other trees of the same species. Subsequent chemical analysis revealed a higher proportion of toxic or unpalatable substances in the rejected individuals. They are, however, when not given a choice, capable of detoxifying the toxic plant secondary metabolites, though at a cost of higher energy and nitrogen requirements.
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