Abnormal behaviour in captive animals is both pervasive and ambiguous. Although individual differences are central to the field of animal welfare, studies on abnormal behaviour predominantly employ quantitative, population-level approaches. For example, whereas previous studies on chimpanzee (Pan troglodytes) abnormal behaviour have reported significant variation between groups or individuals in the quantity (eg frequency and duration) of abnormal behaviour, much less is known about qualitative differences. Individual abnormal behavioural repertoires may be highly idiosyncratic, where certain behaviours are over-represented (ie individually specific abnormal behavioural ‘signatures’). The present study investigated qualitative individual variation in the abnormal behaviour of chimpanzees (n = 15) housed at Royal Burgers’ Zoo in Arnhem, The Netherlands. Substantial variation was found between individuals in the diversity (size and evenness) and overall composition of their abnormal behavioural repertoires. Factors including age, sex, and rank did not significantly account for dissimilarity of individuals’ abnormal behavioural repertoires, but kin dyads showed more similar abnormal behaviour than non-kin dyads. Further exploratory analyses examined whether individual variation in one abnormal behaviour (coprophagy) predicted variation in stress-related behaviour (self-scratching). This allowed us to tentatively conclude that there were also individual differences in the link between a given abnormal behaviour and the behavioural expression of stress. Qualitative individual variation in abnormal behaviour provides a novel angle to a literature traditionally focused on quantifying abnormal behaviour at the group- or species-level and may thus represent an important yet previously overlooked source of variation in the extent to which abnormal behaviour reflects the state of individual welfare.

Worldwide, farm animals are kept on litter or foraging substrate that becomes increasingly soiled throughout the production cycle. For animals like laying hens, this means that it is likely they would scratch, forage and consume portions of excreta found in the litter or foraging substrate. However, no study has investigated the relative preference of laying hens for foraging and consumption of feed mixed with different percentages of excreta. A total of 48 White Leghorn laying hens of two strains, a commercial strain (Lohmann LSL-Lite (LSL), n=24) and UCD-003 strain (susceptible to liver damage, n=24), were individually housed and given access to feed mixed with increasing percentages of hen excreta (0%, 33%, 66% and 100% excreta diets) and corn as a luxury food reward (four corn kernels per diet daily). The amount of substrate and number of corn kernels consumed from each diet was recorded for a period of 3 weeks. Both LSL and UCD-003 hens preferred to consume and forage in diets with 0% excreta, followed by 33% and finally diets containing 66% and 100% excreta. Despite the presence of excreta-free diets, birds consumed on average 61.3 g per day of the diets containing excreta. Neither physical health, measured by plasma enzyme activity levels, nor cognitive differences, assessed by recalling a visual discrimination task, was associated with relative feeding or foraging preference. In conclusion, this study demonstrated a clear preference for feeding and foraging on substrate without excreta in laying hens. However, considering the amount of excreta diets consumed, further studies are needed to understand the causes and consequences of excreta consumption on physiological and psychological functioning, and how this information can be used to allow adjustments in the management of foraging substrates in farmed birds.

New Zealand fur seals (Arctocephalus forsteri) forage mostly in open waters at night and spend parts of the day in coastal sheltered sites, where they may play, rest and eliminate wastes. We recorded the purple wrasse (Notolabrus fucicola) feeding on faeces and vomits of these pinnipeds at Fortescue Bay in the Tasman Peninsula, Australia. This behaviour allows the wrasse to get nutrients from open waters that otherwise would not be available. Thus, it is suggested that the fur seals have the role of transferring nutrients from open waters to inshore reefs and provide them as particulate food to fish. This functional role is apparently recorded for only one species of marine mammal so far, the spinner dolphin (Stenella longirostris), in tropical oceanic waters.

Larvae of Lepidoptera are mainly herbivores, and only the larval stages of Bradypodicola and Cryptoses pyralid moths are known to be specialized coprophages. Here, we report coprophagy as a main feeding habit for the larvae of another pyralid moth, Aglossa pinguinalis, on the basis of observational and experimental evidence. The larvae of this moth require two years to complete development, and construct silk tubes connecting the food source with a shelter chamber. Larvae of A. pinguinalis were mostly found inside caves, where they were about 700 times more abundant than in the open field. Inside the caves, observational results indicate that 98% of the larvae fed mostly on excrement and only 2% were recorded as eating other kinds of detritus (decayed mushrooms). No larvae were recorded eating plant detritus in the censuses nor in experimental detritus patches. The larvae did not show preferences for different types of excrement in the caves. Experimental dog and sheep excrement corroborated this result, showing that the abundance of larvae did not differ between these two excrement types over the entire study. We suggest that habitat selection of A. pinguinalis is ecologically similar to the trophic specialization of Bradypodicola and Cryptoses, in spite of the differences in natural history traits among these moths. Feeding on dry excrement inside caves, or in buried sloth dung, may reflect the constraints for Lepidoptera successfully to colonize excrement: in more exposed excrement, they cannot compete with other coprophagous specialists owing to the lack of parental care (e.g. resource relocation) and slow growth rates. We hypothesize that coprophagous Lepidoptera will be restricted to competition- and predation-free habitats and resources, feeding on excrement inside caves and animal burrows.

Four rats were housed in cages with mesh floors; another four rats were housed in tubular anti-coprophagy cages, in which they could not turn round to reach their own faeces. Both groups were fed for 6 d on a low-protein diet containing fermentable carbohydrates and 15NH4Cl. At the end of the experiment the rats were killed and their carcasses were homogenized, lysine was isolated by ion-exchange chromatography and its 15N enrichment measured by isotope-ratio mass spectrometry. The 15N enrichment in the lysine of the microbial fraction of faeces and the total amount of lysine in the body were also determined in order to estimate the amount of microbial lysine absorbed. The 15N enrichment in body lysine of non-coprophagic rats was not different from that previously measured in rats given unlabelled NH4Cl, but in coprophagic rats it was significantly higher. The daily absorption of microbial lysine by the coprophagic rats accounted for 20·7 (SE 2·55) mg/kg body weight0·75 but was only 0·5 (SE 1·04) mg/kg body weight0·75 for the non-coprophagic rats. This value was not significantly different from zero. The utilization of microbial amino acids via coprophagy resulted in a higher weight gain (adjusted for intake) in the coprophagic group (15·5 g/6 d) than in the non-coprophagic rats (3·1 g/6 d). It was concluded that, in rats, the utilization of microbial lysine occurred exclusively via coprophagy.

We developed a new type of anal cup for prevention of coprophagy and determined whether the absorption of Ca and Mg and the stimulatory effects of feeding fructo-oligosaccharides (FO) on theabsorption of Ca and Mg were altered by prevention of coprophagy in rats. Rats were fed on a FO-free diet or a diet containing 50 g FO/kg for 2 weeks with or without prevention of coprophagy. FO-feeding increased the apparent absorptive ratio of Ca and Mg in rats with or without prevention of coprophagy. However, in the FO-fed groups the absorptive ratio of Mg in rats with prevention of coprophagy was higher than in rats withont prevention of coprophagy. The Ca content of the femur was higher in rats fed on the FO-diet than in rats fed on the FO-free diet both with and without coprophagy. In conclusion, FO-feeding increased the absorption of Ca and Mg in rats both with and without coprophagy. Moreover, prevention of coprophagy enhanced the absorption of Mg in rats fed with FO. Coprophagy has to be considered when the effects of luminal fermentation or mineral absorption are examined in rats

Male rats were fed on either a non-purified rodent diet (JS) or cholesterol-free purified diets containing wheat bran (WB) or oat bran (OB). Some animals were allowed normal access to their faeces for coprophagy (coprophagy +), while in others coprophagy was prevented by placement of a plastic cup over the anus (coprophagy −). Direct ingestion of faeces from the anus was observed in the former groups. Food intake was unaffected by diet or coprophagy status and body weight gain was unchanged with OB − and JS − but was significantly lower with WB −. Plasma cholesterol was highest with WB and equally lower with OB and JS and was unaffected by coprophagy status. Plasma triacylglycerols were highest with OB and were unaffected by coprophagy status. Caecal digesta mass was highest with JS, intermediate with OB and lowest with WB. Digesta mass was unaffected by coprophagy status with WB and JS but was higher with OB −. Digesta moisture content was lowest with WB + but highest with WB −. Digesta volatile fatty acid (VFA) concentrations were similarly lower with OB + and OB −, but were significantly lower with JS − and WB − than in the corresponding coprophagy + group. In all groups digesta butyrate concentrations were reduced by coprophagy prevention. Pools of total VFA, acetate and butyrate in the digesta were highest with JS. Pools of total VFA in digesta were highest with JS +, OB + and OB − and lowest with WB + and WB −. The propionate pool was highest with OB −, intermediate with OB +, and equally low in all other groups. The pool of butyrate was highest with JS + and lowest with OB −. Effects of oats and wheat on plasma cholesterol in the rat do not seem to be mediated through faecal re-ingestion.

Six boars weighing about 65 kg were penned individually in preliminary observations to investigate their response to increasing levels of faeces in a concentrate diet fed as a gruel. During an introductory 5-day period pigs were restricted to 1·5 kg concentrates plus 100 g fresh faeces daily. The daily concentrate allowance was then increased to 2·2 kg and faeces increased by 50 g/day providing the ration was consumed completely. Two animals showed diarrhoea at intakes of 1 kg faeces per day while the remaining four animals showed no signs of ill health at the maximum allowance of 1·4 kg faeces per day.

In the main experiment littermate pairs of the same sex (16 boars plus 16 gilts in total) were allocated to control (concentrates only) or treated (concentrates plus fresh faeces) groups. Animals were housed in metabolism crates from about 55 kg live weight and the diet allowances were increased gradually up to 2·5 kg concentrates with or without 500 g fresh faeces per day. This was achieved on day 17 and continued to slaughter some 40 days later when pigs weighed around 85 kg live weight. Levels of skatole and indole were significantly higher in the caecal contents of treated pigs at slaughter but similar in faeces compared with controls. There was no effect of dietary treatment on skatole or indole levels in subcutaneous fat.

It seems unlikely that natural coprophagy would contribute significantly to skatole and indole levels in carcass tissues.

The quantity of re-ingested faeces was calculated by comparing faecal dry matter of unrestricted rats and coprophagy-restricted rats after correcting for differences in food intake. Due to high day-to-day variations of produced and re-ingested faeces it was not possible to calculate precisely the extent of coprophagy of an individual rat at a particular day with this difference method. Reliable quantitative estimates require at least two rats and a collection period of 7 d. When fed on a nutritionally complete diet, rats re-ingested 0-11 % of their faeces. When fed on low-protein diets (66 g egg albumin/kg) or diets diluted with 200 g cellulose/kg, coprophagy was not significantly increased. A high re-ingestion rate (6–25 %) was observed with thiamin and pantothenic acid deficiencies. After re-ingestion of faeces had been prevented for 1 week, the amount of faeces re-ingested during the subsequent week without tail-cups was increased twofold. It is concluded that rats are able to regulate the amount of faeces eaten precisely according to their requirements.