Social enhancement for caged macaques: 80-92


 Feeding enrichment promotes
non-injurious foraging and/or food processing activities

Macaques will work for food even when identical food is freely available [Anderson & Chamove, 1984; Evans et al., 1989; Line et al., 1989b; O'Connor & Reinhardt, 1994]. This suggests that they have a need to get actively involved in the food acquisition process. In the laboratory, this need is usually not met because food is offered in such a way that no or little effort is required to collect and process it [Bartecki, 1993].



Photos 80 & 81: When given the choice of:

(1) collecting their daily ration of 33 biscuits from the ordinary, freely accessible food box (photo 80), and/or
(2) working for the retrieval of the same biscuit ration from a food puzzle, i.e., food box remounted and bolted directly onto the mesh, away from original large access hole (photo 81),

eight adult rhesus males spent on average:

(1) 0.5 minutes collecting 29 biscuits from the food box, and
(2) 11.2 minutes retrieving 11 biscuits from the food puzzle during 60-minute test sessions [Reinhardt, 1994d].

They consumed all the biscuits (11) for which they had worked, but only 52% of the biscuits (15) which they had hoarded without effort.




Photos 82* & 83*: Offering the daily biscuit ration in the food puzzle instead of in the ordinary food box results in a more than 100-fold increase in time devoted to food gathering behavior - i.e., foraging behavior - in pair-housed rhesus [Reinhardt, 1993a].

In a study with 158 rhesus monkeys, 89% of the animals accepted the food puzzle as primary feeder. The remaining 11% did not retrieve enough biscuits (e.g., because of dental problems making it difficult to pull biscuits through the mesh). Their food puzzle was reconverted into a normal food box, to assure unrestricted access to the food [Reinhardt, 1993b].
In one remarkable case, a blind, pair-housed rhesus female learned to use the food puzzle, and she retrieves her daily biscuit ration as skillfully as other animals do [Reinhardt & Garza-Schmidt, 2000].

Working for their standard food rather than collecting it from freely accessible food boxes does not impair the animals' body weight maintenance [Reinhardt, 1993b,e; Murchison, 1994; Bertrand et al., 1999].

It may not always be possible to create a food puzzle by simply remounting the food box; different cage modules may require different modifications to make the removal of biscuits a more time consuming activity for the animals [e.g., Murchison, 1994,1995; Reinhardt & Garza-Schmidt, 2000].

The food puzzle is a structural element of the cage, re-designed to serve as primary feeder. Therefore, no extra time is needed to clean it and bait it with special food items.

  Photo 84*: The usefulness of the food puzzle as permanent, primary feeding enrichment device has been confirmed in stump-tailed macaques (M. arctoides; photo 84; Reinhardt 1993c), Japanese macaques (M. fuscata; Yanagihara et al., 1994) and long-tailed macaques (M. fascicularis; Reinhardt & Garza- Schmidt, 2000).


Photo 85: A variety of custom-made
[e.g., Line & Houghton, 1987; Bramblett & Bramblett, 1988; Moazed & Wolff, 1988; Markowitz & Line, 1989;
Gullekson et al., 1991; Kaplan & Lobao, 1991; Lam et al., 1991; Murchison, 1991,1992; Bayne et al., 1991,1992; Clark, 1992; Murchison & Nolte, 1992; Bartecki, 1993; Holmes et al., 1994; Taylor et al., 1994; Niemeyer et al., 1998] and commercial foraging devices - such as this puzzle feeder [e.g., Bloom & Cook, 1989] - for macaques have been described. They are relatively expensive and require extra labor time to load and clean them [Bayne et al., 1993].

Little published information is available on the long-term usefulness of these devices [Reinhardt, 1993d].




Photos 86* & 87*: The 'ceiling puzzle' is probably the least expensive foraging 'device'.

Placing the daily biscuit ration on the ceiling of the cage - instead of in the food box - requires no extra material and no extra personnel time, but it induces an 80 to 290-fold increase in foraging time, depending on the shape of the biscuits [Reinhardt, 1993e].

Monkeys tend to hoard food when they have free access to it. It is common for a rhesus macaque, for example, to get hold of as many biscuits as possible at the moment of feeding, fill both cheek pouches to the brim, hastily grab the remaining biscuits from the food box and drop most of them on the floor, and only then start consuming biscuits. Inevitably, some biscuits lying on the floor get in contact with feces and/or urine and are consequently rejected by the animal. Care staff have to remove these discarded biscuits from the cage to prevent the development of mold in the corners of the cage. This problem does not exist in the ceiling puzzle and food puzzle situation: There is no hoarding; once a biscuit has been laboriously retrieved, it is quickly consumed [Reinhardt, 1993a,e; Murchison, 1994,1995]. It may happen that fragments of biscuits fall down in the course of the foraging process, but they are usually so small that they pass through the mesh of the floor to be flushed away in the drop pan. The cages of animals who get involved in the foraging process are distinguished by the absence of spoiled food [Reinhardt, 1993e; Reinhardt & Garza-Schmidt, 2000].

Photos 88* & 89: Produce of the season introduces some variety into the monotonous standard feeding regimen. It would be a waste of time chopping fruits and vegetables for the animals [cf. Smith et al., 1989]; they have all the time needed and seemingly enjoy processing the food themselves.

Every macaque should receive at least one whole fruit - such as an apple (photo 88) - or one whole vegetable - such as corn on the cob (photo 89) - on a daily basis. Who could argue that the animals do not deserve these special treats?

Photos 90 & 91 When seasonal produce is not available, ice cubes (photo 90; cf. McNulty, 1993) or peanuts in the shell (photo 91) provide a welcomed substitute.



Photo 92: Handing food treats directly to the animals not only provides another option of feeding enrichment but it also offers a simple way to promote and foster a positive human-animal relationship. The beneficial effect of this 'technique' is reflected in the fact that rhesus macaques show a reduction of behavioral disorders not only while treats are handed out but also later, on days when they receive no treats [Bayne et al., 1993]. This carryover phenomenon has not been observed when monkeys receive foraging devices [Watson, 1992; Bayne et al., 1993; Novak et al., 1998], demonstrating that caregivers play a crucial role in safeguarding the well-being of the animals [cf. Wolfle, 1987; NRC, 1998].

  Inanimate Enrichment (photos 93-108)

  Table of Contents

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