Bedding as an Enrichment Strategy in Group-housed Mauritian Cynomolgus Macaques (Macaca fascicularis)

Abstract

The research community is committed to improving the well-being of nonhuman primates by providing opportunities to express species-specific behaviors such as foraging. In the wild, macaques spend a large part of their day foraging; this behavior is greatly limited in captivity. Bedding (wood shavings substrate) has been shown to promote foraging in rhesus macaques. However, the amount of bedding needed to affect these changes is unknown. Further, few studies have examined other benefits of bedding, including its potential to reduce noise levels, which can negatively impact welfare. We examined the use of bedding substrate in male Mauritius cynomolgus macaques (2-3-y-old) living in one of 2 social groups with either a full bale of bedding (that is, approximately 6 in of substrate) or a half bale (approximately 3 in) added to the pens for 10 d, followed by 4 d without bedding. We performed focal observations on 8 monkeys biweekly for 8 wk and used a dosimeter to measure sound in the room for 42 d. As expected, monkeys spent significantly more time foraging and less time self-grooming when bedding was present than when it was not. The amount of bedding did not make a difference. The presence of bedding did not affect social grooming or aggression, although it did help to dampen sound. Both peak and mean sound levels were lower with a full bale of bedding than with no bedding. Taken together, these results suggest that bedding is an effective enrichment strategy that can improve welfare of group-housed macaques.

Figure 1.

Flexible pen housing (Carter2Systems, Hillsboro, OR) without bedding (A) and with a full bale of bedding (B). The pens contained verandas, climbing structures, perches, and other platforms. Each side of the room housed 1 group of either 12 or 14 macaques. When bedding was not present, other enrichment items such as Ferris wheels or pools were placed on the floor.

Figure 2.

Timeline of study. Bedding (half or full bale per pen) was placed in the pens for 10 d and then removed for 4 d.

Figure 3.

Ethogram of behaviors coded during observations of cynomolgus macaques.

Figure 4.

Percent of intervals in which the focal macaques were foraging with a full bale per pen, half bale per pen, or no bedding present.

Figure 5.

Percent of intervals in which focal animals were self-grooming with a full bale per pen, half bale per pen, or no bedding present.

Figure 6.

The mean (A) and peak (B) sound recorded in the room with a full bale per pen, half bale per pen, or no bedding present. Normal human conversations are generally around 60dB.