Simal, F.

The Island of Bonaire possess a system of more than 150 natural caves, but only five of them are known to be used as diurnal and maternity roosts by the five species of cave-dwelling bats reported for this island. In the case of Natalus tumidirostris and Myotis nesopolus, Pos di Antoin is the only one. Additionally, this cave is the most important maternity roost known on Bonaire for Glossophaga longirostris and it is also used by all the species of cave-dwelling bats recorded on Bonaire. Its certification as SICOM will become crucial to support and reach the goal of changing its designation status in the Zone Planning to “Natural Area” and/or “Protection Zone-Cave”, in addition of providing this roost with adequate legislation and management plans for its protection. Besides this, its certification will complement the AICOMs and SICOMs already certified on the ABC islands.

The Openbaar Lichaam Bonaire, virtually all nature organizations, private companies and most individuals on Bonaire recognize caves as important features in the landscape and are aware of one or several of their values. Attempts to implement proper protection and management have been conducted with different degrees of success in the past. However, a financially sustainable and efficient management system has not been proposed yet and there is no indication of any significant efforts toward these goals currently ongoing. Successful conservation of caves on Bonaire can only be achieved through the integration of multiple disciplines, institutions and people, organized by means of a strategic plan.

Currently, the ecological, scientific, recreational, cultural and touristic values contained in caves are threatened by uncontrolled activities, both of legal and illegal character. There is virtually a complete lack of management and supervision of the activities happening in the Bonaire caves today. Illegal dumping of solid and liquid waste, uncontrolled visits and “off the record” exploration and documentation efforts by different personal initiatives are a few examples that illustrate this situation. Most importantly, despite their ecological importance, bat populations on Bonaire are threatened by uncontrolled visits to caves that they use as maternity chambers.

Overall Objective

To create the Bonaire Caves and Karst Nature Reserve in order to provide optimum protection and management for the natural, cultural, recreational and scientific values contained in the Bonaire Cave System by September 2019.

Project purpose

• To protect, conserve and restore (if applicable) the natural, cultural, historic, esthetic, recreational and scientific values contained in the cave systems of Bonaire, including, but not limited to, the native flora and fauna, the speleological formations and the ancient inscriptions for future generations,
• To restore the native vegetation of Bonaire,
• To ensure a viable population of 5 keystone species for the island and their ecological interactions,
• To ensure that the residents of, and visitors to Bonaire receive a quality education and information about the ecological importance and protection of caves and the values contained in them,
• To promote and ensure that the resources contained in this cave system are used in a sustainable manner
• To ensure that human safety is given priority during all cave related activities.

Impact project en borging resultaten

For the implementation of the Bonaire Caves & Karst Nature Reserve, the political will of local decision-makers is key. In order to include this implementation on their agenda, lobbying from different sectors is essential, being the most important ones the Dutch Government, universities and research institutions, nature-funding organizations (e.g. WWF, DierenLot and Postcode Loterij), local nature organizations and, last but not least, the local tourism sector guided by the TCB office.

For conducting the necessary research and monitoring of bat populations and other species protected by local legislation inhabiting caves and karst environments (e.g. candle cacti, barn owl, Yellow-shouldered parrot and pearly-eyed thrasher) only funding is needed. The expertise is For conducting the necessary research and monitoring of bat populations and other species protected by local legislation inhabiting caves and karst environments (e.g. candle cacti, barn owl, Yellow-shouldered parrot and pearly-eyed thrasher) only funding is needed. The expertise is locally available and research and monitoring for the species above mentioned are either irregularly ongoing due to lack of funds or a written plan already exists. CARIBSS will propose to implement a fee system, similar to one of the national parks, for the use of these areas. Lastly, for fencing the complete park, only funds are needed as well. Approximately USD 20,000.00.

The Island of Bonaire has a system of natural caves that probably exceeds 150 in number. Those caves house at least five species of bats: Leptonycteris curasoae, Mormoops megalophylla, Natalus tumidirostris, Myotis nesopolus and Glossophaga longirostris. The former four depend primarily or exclusively on caves as diurnal and maternity roosts. The IUCN Red List of Threatened Species considers L. curasoae as Vulnerable. Several studies have underlined the importance of this bat as a pollinator and long-distance seed dispersal agent of several species of succulent plants in northern South America. Likewise, indirect evidence suggests that between December and March part of the populations of Aruba, Curaçao and Bonaire abandon these islands and move to the arid and semiarid zones of Venezuela and Colombia. Until now, we did not know that L. curasoae reproduced on Bonaire, but during the last three years, studies conducted on the island have shown that it is important as a mating and maternity site for the species. At present, we have identified four caves used as maternity roosts. Mormoops megalophylla also reproduces on Bonaire, with at least two maternity caves. Recognition of the Washington–Slagbaai National Park and surrounding areas as an AICOM will contribute to protecting the main habitat types used by all species present on the island as food sources and roosts.

Located in the South Caribbean xeric region, approximately 800 m from the Island of Bonaire, Klein Bonaire is a small flat island (maximum elevation 7 m a.s.l.) with a surface of 690 ha of limestone of coral reef origin and an estimated age of 30.000 to 40.000 years. Free of herbivorous exotic species since the 1980s, it presents a dry thorny forest dominated in the central area by columnar cacti of two species, Stenocereus griseus, and Cereus repandus. These cacti have high production of flowers and fruit, suggesting high foraging activity of the two nectar-feeding bats that live on Bonaire Island, Glossophaga longirostris, and Leptonycteris curasoae. Ecological interactions established between these bats and the cacti (pollination and seed dispersal) are essential for the maintenance of the dry ecosystems present on Bonaire. In addition, the bat pollinated tree Crescenta cujete is also a common species in the plant community. Other species on the island use its fruits. Because of the short distance that separates Bonaire and Klein Bonaire, the second is an important source of food resources for L. curasoae, known to fly over seawater. As natural habitats of Bonaire, including protected areas, undergo a degradation process due to the negative impact of exotic herbivore mammals (goats, sheep, donkeys, and pigs) and the land suffers a fragmentation process due to touristic and urban developments, the importance of Klein Bonaire as food reservoir for fruit bats increases. This island is free of exotic herbivores, and the construction of any type of residential structure is forbidden. Despite being already considered a protected area locally and internationally, its designation as AICOM is important for several reasons: a) it will help enforce future management plans for the island in favor of its wildlife, b) it will influence the approval of future environmental projects on the island (e.g., reforestation, research, recreational activities), c) it will enforce the need to protect the island, d) it will facilitate its designation as a KBA (Key Biodiversity Area) and, e) it will complement the current system of AICOMs and SICOMs recognized for the ABCs.

The Island of Bonaire possess a system of more than 150 natural caves, but only five of them are known to be used as diurnal and maternity roosts by the five species of cave-dwelling bats reported for this island. The Curaçaoan Long-nosed bat (Leptonycteris curasoae) uses all five, but only two of them are used by the Ghost-faced bat (Mormoops megalophylla). Leptonycteris curasoae is one of the two nectar-feeding species responsible for pollination and seed dispersal of columnar cacti in Aruba, Curaçao and Bonaire. This species has been classified as Vulnerable in the IUCN Red List of Threatened Species. Both L. curasoae and M. megalophylla depend on caves as diurnal roosts. Altogether, these attributes reflect clearly the great importance of providing special protection to the caves used by these species. Of the two maternity roosts shared by both species, Kueba di Watapana has demonstrated to be the most important, because it contains one of the largest colonies of pregnant and lactating females of L. curasoae during the reproductive period. Unfortunately, this cave is outside the limits of the protected areas on Bonaire. Its designation as SICOM will contribute to set the basis for adequate management plans and a protective legislation that secures the integrity of this roost and the colonies of L. curasoae and M. megalophylla present in them. The most positive direct impact of this SICOM will be the protection of gravid females of L. curasoae and their newborns. Finally, its designation as a SICOM will complement the AICOM already created.

Brown Boobies (Sula leucogaster) are known to roost on the northwestern coast of Bonaire, Caribbean Netherlands. A published account from the 1950s reported ~200 Brown Boobies roosting in this area, along with smaller numbers of two other seabird species, and described regular hunting raids by fishermen in which up to 100 birds were harvested. In 1969, this roosting area and its surroundings were designated as a 30-km² nature reserve, and hunting became illegal. Although seabird assemblages were not monitored subsequently, anecdotal reports suggest that the number of roosting seabirds had decreased dramatically to < 60 individuals. In 2008–2010, we conducted roost counts at seven sites in Washington-Slagbaai National Park in northwestern Bonaire. Most counts were substantially higher than the anecdotal reports, with a maximum of 240 Brown Boobies in July 2009. We saw no evidence of breeding and did not observe any banded birds. Other roosting birds—Masked Boobies ( Sula dactylatra) and Brown Noddies (Anous stolidus)—were also present in very small numbers.

Keywords

Bonaire, Brown Booby, Caribbean Netherlands, citizen science, roost, Sula leucogaster, Washington-Slagbaai National Park

Green turtles Chelonia mydas and hawksbill turtles Eretmochelys imbricata are neg- atively impacted by natural and anthropogenic disturbances. Unknown numbers of turtles are killed annually in the coastal waters of Bonaire and Klein Bonaire, Caribbean Netherlands. We used N-mixture models, conventional distance sampling and the multiple Lincoln-Petersen method to estimate abundance from transect-count and net-capture surveys. Maximum likelihood and Bayes- ian generalised linear models were used to assess trends in annual abundance in 2003−2018, and a Bayesian state-space logistic model was developed to generate the posterior distributions of pop- ulation parameters and make abundance predictions for 2019−2030. Mean ± SE annual abun- dance was 555 ± 149 green turtles (2.5th and 97.5th percentiles = 337, 943) and 70 ± 13 hawksbill turtles (49, 101), and there were no trends in western Bonaire and Klein Bonaire in 2003−2018. Mean annual abundance was 348 ± 135 green turtles (171, 731) and there was a positive trend inside Lac Bay, southeast Bonaire, 2003−2018. Green turtles have higher population growth rate and carrying capacity, and therefore can sustain higher human-induced mortality than hawksbill turtles. However, under low mortality rates (<0.100), both species can fluctuate stably between the lower and upper limits of the carrying capacity. The methodology implemented can be adapted to estimate sea turtle abundance, monitor and model their population dynamics, and assess the neg- ative impact of human-induced mortality in other Caribbean islands.

KEY WORDS: Chelonia mydas · Eretmochelys imbricata · Abundance · N-mixture model · Distance sampling · Multiple Lincoln-Petersen method · Generalised linear model · Bayesian state-space logistic model

Abundance estimates based on adequate survey design and count methodology are needed for population monitoring and modelling, and for assessing the results of conservation actions taken to boost or maintain population size at desired target levels. We monitored Bonaire’s population of yellow-shouldered parrot Amazona barbadensis rothschildi using systematic distance sampling surveys in 2009–2017, and developed a Bayesian state-space logistic model to predict changes in abun- dance resulting from increased human-induced mortality in 2018–2066. Survey-based abundance estimates (mean ±bootstrapped SE) were 0.172 ± 0.020 parrots ha–1 and 2924 ± 340 parrots at a survey region covering 17 000 ha. Model- based posterior distribution estimates (mean ± MCMC SD) of maximum population growth rate, maximum sustainable mortality rate, maximum sustainable mortality, population carrying capacity and equilibrium population size were 0.179 ±0.129, 0.090 ± 0.064, 219 ± 135, 5623 ± 2043 and 2811 ± 1022 parrots. With low to moderate mortality rates (0.001– 0.100, 0.101–0.250), predicted population sizes (mean ± MCMC SD) were 2963 ± 668 and 2703 ± 1660 parrots in 2018, and 2754 ± 690 and 2297 ± 1301 parrots in 2066. With high mortality rates (0.251–0.500), predicted population sizes were 1780 ± 1160 parrots in 2018 and 26 ± 139 parrots in 2066. Because the relative importance and magnitude of human–parrot conflicts are unknown but may be unsustainable, we consider the parrot population vulnerable to the risk of extinction during the modelled time horizon. Therefore, we recommend long-term monitoring and modelling for assessing changes in abundance and the results of conservation actions taken to keep the population above 2800 parrots in the survey region (i.e. population size N > 2.5% percentile of the posterior distribution of population carrying capacity K).

As pollinators of the typical dry forest cacti, bats are a keystone species. Dry tropical forests are the most threatened type of forest in the Dutch Caribbean due to positioning close to built-up areas. The bats use the many caves as resting habitat. A map of the caves on Bonaire can be found here.

A baseline study on the 9 species of bats of Bonaire (2008-2014) ran across 11 sites and provides information on abundance, sex, weight, size, etc.

Mist netting at caves data:

• Cave use dynamics of cave-dwelling bats in the islands of Aruba, Curaçao and Bonaire
• Population estimates of cave-dwelling bats of in the islands of Bonaire, Aruba and Curaçao

Mark and recapture data:

• Long flights and migratory movements in the South Caribbean of the Curaçaoan Long-nosed bat (Leptonycteris curasoae)

Mist netting, harp traps and ultrasound detector data (bats voice calls):

• Use of habitat types by the bat fauna of Bonaire 

Please contact the DCBD admin, WILD conscience, or STINAPA for more information.

Detailed 3D maps of known Bonairian cave systems.

Caves are especially found in relative soft calcareous rock dissolving and eroding as a result from water and wind. Bonaire exists for roughly 1/3 of volcanic rock and 2/3 of calcareous rock (see geological map). Through time hundreds of dry and wet caves were formed. Cave systems in the Caribbean contain key ecological, cultural, esthetic, scientific and recreational values, including bat resting and  maternity roosts. Bats are a keystone species for dry  tropical forest (see Simal et al., 2015).

Please contact the DCBD admin, WILD conscience, or CARIBBS for more information.