7.8. Threat: Invasive and other problematic species and genes

7.8.1 Problematic animal/plant species and genes

No evidence found (no assessment)

1We have captured no evidence for the following interventions:

  • Reduce primate predation by non-primate species through exclusion (e.g. fences) or translocation
  • Reduce primate predation by other primate species through exclusion (e.g. fences) or translocation
  • Control habitat-altering mammals (e.g. elephants) through exclusion (e.g. fences) or translocation
  • Control inter-specific competition for food through exclusion (e.g. fences) or translocation
  • Remove alien invasive vegetation where the latter has a clear negative effect on the primate species in question
  • Prevent gene contamination by alien primate species introduced by humans, through exclusion (e.g. fences) or translocation.

7.8.2 Disease transmission

Trade-off between benefit and harms

● Preventative vaccination of habituated or wild primates

2Three before-and-after studies in the Republic of Congo and Gabon, two focusing on chimpanzees and one on gorillas, found that most reintroduced individuals survived over 3.5-10 years after being vaccinated, alongside other interventions. One before-and-after study in Puerto Rico found that annual mortality of introduced rhesus macaques decreased after a preventive tetanus vaccine campaign, alongside other interventions. Assessment: trade-offs between benefits and harms (effectiveness 70%; certainty 40%; harms 30%).

3https://www.conservationevidence.com/​actions/​1549

Unknown effectiveness (limited evidence)

● Wear face-masks to avoid transmission of viral and bacterial diseases to primates

4One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being visited by researchers and visitors wearing face-masks, alongside other interventions. One study in Uganda found that a confiscated chimpanzee was successfully reunited with his mother after being handled by caretakers wearing face-masks, alongside other interventions. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 5%; harms 0%).

5https://www.conservationevidence.com/​actions/​1537

● Keep safety distance to habituated animals

6One before-and-after study in the Republic of Congo found that most reintroduced chimpanzees survived over five years while being routinely followed from a safety distance, alongside other interventions. One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being routinely visited from a safety distance, alongside other interventions. However, one study in Malaysia found that orangutan numbers declined while being routinely visited from a safety distance. Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).

7https://www.conservationevidence.com/​actions/​1538

● Limit time that researchers/tourists are allowed to spend with habituated animals

8One before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being routinely visited during limited time, alongside other interventions. One controlled study in Indonesia found that the behaviour of orangutans that spent limited time with caretakers was more similar to the behaviour of wild orangutans than that of individuals that spent more time with caretakers. Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).

9https://www.conservationevidence.com/​actions/​1539

● Implement quarantine for primates before reintroduction/translocation

10Six studies, including four before-and-after studies, in Brazil, Madagascar, Malaysia and Indonesia have found that most reintroduced primates did not survive or their population size decreased over periods ranging from months up to seven years post-release, despite being quarantined before release, alongside other interventions. However, two before-and-after studies in Indonesia, the Republic of Congo and Gabon found that most orangutans and gorillas that underwent quarantine survived over a period ranging from three months to 10 years. One before-and-after study in Uganda found that one reintroduced chimpanzee repeatedly returned to human settlements after being quarantined before release alongside other interventions. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).

11https://www.conservationevidence.com/​actions/​1541

● Ensure that researchers/tourists are up-to-date with vaccinations and healthy

12One before-and-after study in Rwanda, Uganda and the Republic of Congo found that gorilla numbers increased while being visited by healthy researchers and visitors, alongside other interventions. However, one controlled study in Malaysia found that orangutan numbers decreased despite being visited by healthy researchers and visitors, alongside other interventions. Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 10%; harms 0%).

13https://www.conservationevidence.com/​actions/​1546

● Regularly disinfect clothes, boots etc.

14One controlled, before-and-after study in Rwanda, Uganda and the Democratic Republic of Congo found that gorilla numbers increased while being regularly visited by researchers and visitors whose clothes were disinfected, alongside other interventions. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).

15https://www.conservationevidence.com/​actions/​1547

● Treat sick/injured animals

16Eight studies, including four before-and-after studies, in Brazil, Malaysia, Liberia, the Democratic Republic of Congo, The Gambia and South Africa found that most reintroduced or translocated primates that were treated when sick or injured, alongside other interventions, survived being released and up to at least five years. However, five studies, including one review and four before-and-after studies, in Brazil, Thailand, Malaysia and Madagascar found that most reintroduced or translocated primates did not survive or their numbers declined despite being treated when sick or injured, alongside other interventions. One study in Uganda found that several infected gorillas were medically treated after receiving treatment, alongside other interventions. One study in Senegal found that one chimpanzee was reunited with his mother after being treated for injuries, alongside other interventions. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 20%; harms 0%).

17https://www.conservationevidence.com/​actions/​1550

● Remove/treat external/internal parasites to increase reproductive success/survival

18Five studies, including four before-and-after studies, in the Republic of Congo, The Gambia and Gabon found that most reintroduced or translocated primates that were treated for parasites, alongside other interventions, survived periods of at least five years. However, four studies, including one before-and-after study, in Brazil, Gabon and Vietnam found that most reintroduced primates did not survive or their numbers declined after being treated for parasites, alongside other interventions. Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 5%; harms 0%).

19https://www.conservationevidence.com/​actions/​1551

● Conduct veterinary screens of animals before reintroducing/translocating them

20Twelve studies, including seven before-and-after studies, in Brazil, Malaysia, Indonesia, Liberia, the Republic of Congo, Guinea, Belize, French Guiana and Madagascar found that most reintroduced or translocated primates that underwent pre-release veterinary screens, alongside other interventions, survived, in some situations, up to at least five years or increased in population size. However, 10 studies, including six before-and-after studies, in Brazil, Malaysia, French Guiana, Madagascar, Kenya, South Africa and Vietnam found that most reintroduced or translocated primates did not survive or their numbers declined after undergoing pre-release veterinary screens, alongside other interventions. One before-and-after study in Uganda, found that one reintroduced chimpanzee repeatedly returned to human settlements after undergoing pre-release veterinary screens, alongside other interventions. One controlled study in Indonesia found that gibbons that underwent pre-release veterinary screens, alongside other interventions, behaved similarly to wild gibbons. Assessment: unknown effectiveness — limited evidence (effectiveness 50%; certainty 10%; harms 0%).

21https://www.conservationevidence.com/​actions/​1553

● Implement continuous health monitoring with permanent vet on site

22One controlled, before-and-after study in Rwanda, Uganda and the Republic of Congo found that numbers of gorillas that were continuously monitored by vets, alongside other interventions, increased over 41 years. Assessment: unknown effectiveness — limited evidence (effectiveness 60%; certainty 20%; harms 0%).

23https://www.conservationevidence.com/​actions/​1554

● Detect and report dead primates and clinically determine their cause of death to avoid disease transmission

24One controlled, before-and-after study in Rwanda, Uganda and the Republic of Congo found that numbers of gorillas that were continuously monitored by vets, alongside other interventions, increased over 41 years. Assessment: unknown effectiveness — limited evidence (effectiveness 40%; certainty 10%; harms 0%).

25https://www.conservationevidence.com/​actions/​1556

No evidence found (no assessment)

26We have captured no evidence for the following interventions:

  • Implement quarantine for people arriving at, and leaving the site
  • Wear gloves when handling primate food, tool items, etc.
  • Control ‘reservoir’ species to reduce parasite burdens/pathogen sources
  • Avoid contact between wild primates and human-raised primates
  • Implement a health programme for local communities.