9.3.1 Food Presentation

Beneficial

Scatter food throughout enclosure

1Four studies, including one replicated study, in the USA, found that scattering food throughout enclosures increased overall activity, feeding and exploration and decreased abnormal behaviours and aggression. Assessment: beneficial (effectiveness 80 %; certainty 80 %; harms 0 %).

2https://www.conservationevidence.com/actions/1315

Likely to be beneficial

Hide food in containers (including boxes and bags)

3Three studies including two before-and-after studies in the USA and Ireland found that the addition of food in boxes, baskets or tubes increased activity levels in lemurs and foraging levels in gibbons. Assessment: likely to be beneficial (effectiveness 75 %; certainty 50 %; harms 0 %).

4https://www.conservationevidence.com/actions/1316

Present food frozen in ice

5Two studies in the USA and Ireland found that when frozen food was presented, feeding time increased and inactivity decreased. Assessment: likely to be beneficial (effectiveness 60 %; certainty 50 %; harms 0 %).

6https://www.conservationevidence.com/actions/1321

Present food items whole instead of processed

7One before-and-after study in the USA found that when food items were presented whole instead of chopped, the amount of food consumed and feeding time increased in macaques. Assessment: likely to be beneficial (effectiveness 80 %; certainty 50 %; harms 0 %).

8https://www.conservationevidence.com/actions/1323

Present feeds at different crowd levels

9One before-and-after study in the USA found that when smaller crowds were present foraging and object use in chimpanzees increased. Assessment: likely to be beneficial (effectiveness 60 %; certainty 40 %; harms 0 %).

10https://www.conservationevidence.com/actions/1324

Maximise both vertical and horizontal presentation locations

11One controlled study in the UK and Madagascar found that less time was spent feeding on provisioned food in the indoor enclosure when food was hung in trees in an outdoor enclosure. One replicated, before-and-after study in the UK reported that when vertical and horizontal food locations were increased feeding time increased. Assessment: likely to be beneficial (effectiveness 65 %; certainty 50 %; harms 0 %).

12https://www.conservationevidence.com/actions/1328

Trade-off between benefit and harms

Present food in puzzle feeders

13Three studies including two before-and-after studies in the USA and UK found that presenting food in puzzle feeders, increased foraging behaviour, time spent feeding and tool use but also aggression. Assessment: trade-offs between benefits and harms (effectiveness 55 %; certainty 80 %; harms 60 %).

14https://www.conservationevidence.com/actions/1318

Unknown effectiveness (limited evidence)

Present food in water (including dishes and ponds)

15One replicated, before-and-after study in the USA found that when exposed to water filled troughs, rhesus monkeys were more active and increased their use of tools. Assessment: unknown effectiveness (effectiveness 60 %; certainty 30 %; harms 0 %).

16https://www.conservationevidence.com/actions/1320

Present food dipped in food colouring

17One before-and-after study in the USA found that when food was presented after being dipped in food colouring, orangutans ate more and spent less time feeding. Assessment: unknown effectiveness (effectiveness 50 %; certainty 20 %; harms 20 %).

18https://www.conservationevidence.com/actions/1322

Provide live vegetation in planters for foraging

19One replicated, before-and-after study in the USA reported that chimpanzees spent more time foraging when provided with planted rye grass and scattered sunflower seeds compared to browse and grass added to the enclosure with their normal diet. Assessment: unknown effectiveness (effectiveness 80 %; certainty 30 %; harms 0 %).

20https://www.conservationevidence.com/actions/1327

No evidence found (no assessment)

21We have captured no evidence for the following interventions:

• Present food which required the use (or modification) of tools
• Paint gum solutions on rough bark
• Add gum solutions to drilled hollow feeders.

9.3.2 Diet manipulation

Likely to be beneficial

Formulate diet to reflect nutritional composition of wild foods (including removal of domestic fruits)

22Two replicated, before-and-after studies in the USA and UK found that when changing the diet of captive primates to reflect nutritional compositions of wild foods, there was a decrease in regurgitation and reingestion, aggression and self-directed behaviours. Assessment: likely to be beneficial (effectiveness 70 %; certainty 60 %; harms 0 %).

23https://www.conservationevidence.com/actions/1329

Provide cut branches (browse)

24One replicated, before-and-after study in the Netherlands and Germany found that captive gorillas when presented with stinging nettles use the same processing skills as wild gorillas to forage. Assessment: likely to be beneficial (effectiveness 70 %; certainty 50 %; harms 0 %).

25https://www.conservationevidence.com/actions/1332

Provide live invertebrates

26One before-and-after study in the UK found that providing live invertebrates to captive lorises increased foraging levels and reduced inactivity. Assessment: likely to be beneficial (effectiveness 85 %; certainty 50 %; harms 0 %).

27https://www.conservationevidence.com/actions/1333

Provide fresh produce

28One replicated, before-and-after study in the USA found that when fresh produce was offered feeding time increased and inactivity decreased in rhesus macaques. Assessment: likely to be beneficial (effectiveness 60 %; certainty 40 %; harms 1 %).

29https://www.conservationevidence.com/actions/1335

No evidence found (no assessment)

30We have captured no evidence for the following interventions:

• Provide gum (including artificial gum)
• Provide nectar (including artificial nectar)
• Provide herbs or other plants for self-medication
• Modify ingredients/nutrient composition seasonally (not daily) to reflect natural variability.

9.3.3 Feeding Schedule

Likely to be beneficial

Change feeding times

31One controlled study in the USA found that changing feeding times decreased inactivity and abnormal behaviours in chimpanzees. Assessment: likely to be beneficial (effectiveness 70 %; certainty 50 %; harms 0 %).

32https://www.conservationevidence.com/actions/1338

Trade-off between benefit and harms

Change the number of feeds per day

33Two before-and-after studies in Japan and the USA found that changing the number of feeds per day increased time spent feeding in chimpanzees but also increased hair eating in baboons. Assessment: trade-offs between benefits and harms (effectiveness 70 %; certainty 50 %; harms 50 %).

34https://www.conservationevidence.com/actions/1337

No evidence found (no assessment)

35We have captured no evidence for the following interventions:

• Provide food at natural (wild) feeding times
• Provide access to food at all times (day and night)
• Use of automated feeders.

9.3.4 Social group manipulation

Trade-off between benefit and harms

Feed individuals in social groups

36One replicated, controlled study in the USA found that an enrichment task took less time to complete when monkeys were in social groups than when feeding alone. One before-and-after study in Italy found that in the presence of their groupmates monkeys ate more unfamiliar foods during the first encounter. Assessment: trade-offs between benefits and harms (effectiveness 60 %; certainty 50 %; harms 25 %).

37https://www.conservationevidence.com/actions/1343

No evidence found (no assessment)

38We have captured no evidence for the following interventions:

• Feed individuals separately
• Feed individuals in subgroups.