ASA Conservation Grant awarded to: Bristol Zoological Society
Lemur frogs, Agalychnis lemur, are Critically Endangered and the population in Costa Rica represents a unique genetic entity (Gray, 2011). In 2018 the Bristol Zoological Society (BZS) secured a Mohamed bin Zayed Species Conservation Grant to survey the distribution of lemur frogs in Costa Rica. The only naturally occurring population was found in Límon province. In 2019 we approached and secured a partnership with a local conservation charity, the Veragua Rainforest Foundation, at the location of natural occurrence. The IUCN Red List identified threats for A. lemur are chytrid fungus and various forms of habitat destruction. Recent work suggests chytrid is prevalent but with low infection intensities in lowland amphibian communities in Costa Rica (Zumbado-Ulate et al. 2019) therefore likely to be of lower importance here. Habitat loss to anthropogenic encroachment in the premontane regions is likely to have disproportionately affected availability of breeding locations for lemur frogs. Historically there has been complete forest clearance for plantations and cattle ranching, but a contemporary problem is increasing illegal land occupation encroaching on larger forest blocks and protected areas. The current natural range for A. lemur includes recovering secondary forest, breeding is known from a number of identified permanent forest pools at Veragua Rainforest.
Until now only preliminary survey and contact activities have been undertaken for lemur frogs in Costa Rica. We have characterised the call and developed a method of passive acoustic survey as a means of monitoring lemur frogs (Emmett et al., In press). Conservation action is required to safeguard the extant relict population, as well as greater survey effort to understand the extent of occupied range. Informal applications of simple artificial ponds and ‘breeding buckets’ have been shown to be effective for A. lemur at both Veragua Rainforest and a translocated group at the Costa Rica Amphibian Conservation Research Center. A formal application of the creation of breeding habitat in accessible areas can be achieved by forming transects away from the area of known occupation and monitoring colonisation and use. In this way the success of the provision of additional breeding sites will be closely monitored. This will be done with the permission and involvement of the community of the adjacent indigenous reserve. No surveys of this reserve have been performed and this would greatly expand the knowledge of the known range of A. lemur. One additional National Park site, Hitoy Cerere, will also be surveyed as it lies between the population in Costa Rica and the extant occupied range in Panama.
The ASA start-up funding will be instrumental in constructing new breeding habitat and both monitoring the breeding pools as well as expanding the lemur frog surveys into the indigenous reserve. The ASA funding will also contribute substantially to the survey of the additional location at Hitoy Cerere. The Veragua Rainforest Foundation maintains an established working relationship with the local indigenous community.
Where fieldwork is carried out, use of biosecurity protocols following a check/clean/dry protocol will be employed. Boots and clothing will be sanitised between sites. Hands-off working will be observed with no handling of amphibians or entering into water bodies unless unavoidable.
Breeding habitat creation
This will comprise the installation of 20 small permanent water bodies in the known area of lemur frog occurrence. Ten of each of artificial lined pools (~dimensions; 1 x 1m and 0.5m depth) and large plastic half-drums (~dimensions; 0.5 x 0.5 x 0.5m) will be used. Artificial breeding sites will be placed at fixed distances from current breeding locations in five transects of four with 50m intervals between successive pools (therefore the furthest will be 200m from an existing breeding location). Pools will be monitored regularly for presence of spawn, tadpoles, and adult frogs; the undersides of all leaves within two metres above or one metre adjacent to the water will be searched for spawn, tadpoles photographed if possible, and a five minute torchlight sweep made for adults around the pool. All regular monitoring will be done at night. Periodic checks may be carried out during the day to confirm spawn and tadpole counts. Acoustic recorders will be moved between pools at least during the one-year intensive monitoring, in order to obtain relative call counts to compare with colonisation data. Colonisation and abundance data will be used to understand whether the different pool types are equally successful, and the information used to gauge the speed and consistency of colonisation. Additional data on species ecology will also be collected such as the identification of individuals through pictures of nocturnal colouration allowing dispersal and longevity to be assessed.
Information regarding the methodology as well as the data will be made available on the BZS web page for the lemur leaf frog project, as well as being published as a peer-reviewed scientific article.
Indigenous reserve surveys
A local team of guides from the local community will be trained in identification methods of the lemur leaf frog (and other Threatened amphibians native to the reserve). All pools located will be recorded with a GPS and a photograph taken to give a rough approximation of size and state. Standardised searches for five minutes separately for each of; spawn, tadpoles, and adults will be undertaken and photographs taken as appropriate. Photographs and GPS information will be passed onto Veragua Foundation staff each month.
Wider survey of Hitoy Cerere National Park
Only a single region less than ten square kilometres is known to be occupied by lemur frogs in Costa Rica, it is important to identify any other isolated populations. The survey team will identify suitable areas during the day, surveying for lemur frog spawn and tadpoles where pools are found. Suitable habitat is determined to be closed canopy forest containing permanent or semi-permanent bodies of standing water of any size. Nocturnal surveys are torchlight transects across the habitat adjacent to the water body. Transects are walked slowly with at least one stop close to the water during which lights are extinguished in order to listen for lemur frog calls for three to four minutes without disturbance. If a lemur frog call is detected, up to ten minutes of searching is undertaken up to twice per site. In this way multiple sites can be visited in an evening without compromising survey effectiveness.
In locations where suitable breeding areas are found but accessibility is limited/prohibited or with unsuitable terrain for night surveys, passive audio recorders will be left to record for one or more nights. The Veragua Rainforest Foundation has become a partner organisation with Bristol Zoological Society for conservation work involving the lemur leaf frog. The Veragua Foundation is currently writing their conservation and research strategy, including the suggestions and project intentions outlined here for breeding habitat creation. In 2019 we mounted an expedition with a mixed team of the indigenous community, Veragua Foundation staff, and BZS staff and students. During this expedition we discussed further activities, the stipulation from the community being that where community lands are concerned there must be a community member present. The Veragua Foundation has a formal agreement with the community for guiding and collecting audio recorder data, and are able to extend this to include our breeding habitat creation and monitoring. Veragua has previously hosted community events and we intend to run a children’s event to dig a pond in one of the more accessible sites to raise awareness of amphibians, and particularly to highlight biosecurity and human responsibility in relation to amphibian conservation.
Establishing a conservation action plan for the lemur leaf frog is one of the BZS five year objectives; only through regular monitoring of established sites can a baseline of population size be established allowing an informed and effective action plan to be developed.