Punta Mona to Bocas del Toro Archipelago IMMA

Criterion A: Species or Population Vulnerability

This IMMA encompasses the habitat of the Caribbean manatee (Trichechus manatus manatus), recognized as the Antillean manatee by the Society for Marine Mammalogy’s Committee on Taxonomy. The West Indian manatee (Trichechus manatus) as a species is globally assessed Vulnerable on the IUCN Red List (Deutsch and Morales-Vela, 2024), but the Caribbean sub-species is considered Endangered (Morales et al. 2024). At local levels, the Caribbean manatee is also listed and protected as Endangered by the Ministry of Environment of Panama (Resolution N0. DM-0657, 2016). Self-Sullivan and Mignucci-Giannoni (2012) reported population estimates for Panama and Costa Rica at 100 individuals each, with minimum counts of 10 and 30, respectively, suggesting a critical status.

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

The common bottlenose dolphin (Tursiops truncatus) population distributed in the archipelago of Bocas del Toro (BDT)-Panama shows high site fidelity. Mark-recapture analysis based on photo-identification data collected between 2004 and 2013 produced an abundance estimate of 80 individuals (95% CI = 72-87) (May-Collado et al., 2015). An effective population size estimate based on genetic data generated a similar abundance estimate (Ne = 73 individuals; CI = 18.0 – ∞; 0.05; Barragán-Barrera et al., 2017). A small segment of this population (37 individuals) is found in Dolphin Bay, a critical area for foraging and feeding; this segment shows a higher recapture rate compared with the rest of the population in the archipelago (May-Collado et al., 2015). Photo-ID data also show that the smaller dolphin segment in Dolphin Bay is represented by approximately 23 reproductive females producing calves (May-Collado et al., 2015).

Both males and females show high philopatry levels (Barragán-Barrera et al., 2017, May-Collado et al., 2017). This population has low mitochondrial diversity, represented by a unique mtDNA-CR haplotype, which is shared between both females and males, and it is not found anywhere else in the Caribbean (Barragán-Barrera et al., 2015, 2017; Duarte Fajardo et al., 2023). The closest neighbouring population is 35 km west of Bocas del Toro in Gandoca-Manzanillo, Costa Rica. The genetic flow between these two populations is restricted to one migrant every 10 years from Bocas del Toro to Gandoca but not the opposite (Barragán-Barrera et al., 2017). Furthermore, ecological data based on stable isotopes (δ¹³C and δ¹⁵N) and total mercury (THg) measurements suggest this bottlenose dolphin population has exclusively inshore habits, which is also reflected in the low THg levels for both females and males in the Bocas del Toro population (Barragán-Barrera et al., 2019).

Data from several surveys show that a small resident population of Guiana dolphin (Sotalia guianensis) inhabits the waters of Costa Rica between Punta Mona and Changuinola River in Panama. This is one of the two known populations of Guiana dolphins found in Central America (May-Collado et al., 2017).  Using photo-identification data from 2003-2006 Gamboa-Poveda (2009) estimated a population size of about 91 (SD= 10) individuals and a residency rate of 64 photo-identified individuals’ ranged between 3 to 56%. Most recent surveys, conducted between 2022 and 2024 (May-Collado, Palacios and Kiszka, unpublished data), confirmed that there is a high residency of Guiana dolphins in this area, with less than 100 individuals identified. Unpublished data from multiple-year boat surveys between Puerto Viejo (Costa Rica) and Bocas del Toro (Panama) indicate that the Guiana dolphins only occur from Punta Mona on the Costa Rican side to the Changuinola River on the Panama side (May-Collado et al., unpublished data) and remain within 3km from the shore (Gamboa-Poveda, 2009).

Criterion C: Key Life Cycle Activities

Sub-criterion C2: Feeding Areas

The wetland and riverine portions of the IMMA, particularly the San San and Changuinola rivers contain vegetation that provides ideal foraging areas for Greater Caribbean manatees.  The composition of aquatic plants in the IMMA can vary seasonally, however, the abundance seems high to sustain individuals feeding for months and years (Guzman, 2024, unpublished data).

A satellite tagging feasibility study conducted in the San  San  Pond Sak Protected Area in 2012 found the following types of vegetation known to be eaten by manatees in other locations: various shore grasses (Panicum sp., Axonopus sp., and Brachiaria sp.) and small amounts of floating vegetation  (Pistia  stratiotes  and  Nymphoides  sp.),  as  well as red mangrove (Rhizophora mangle) (Gonzalez-Socoloske et al. 2015). Although tagged and released near the coastal waters of the estuary, the locations transmitted from the tagged individual female manatee from February 1 to March 17, 2008 showed that the most intensely used areas were in inland portions of the San San and Rio Negro Rivers (Gonzalez-Socoloske et al. 2015) and the authors conclude that this freshwater/brackish vegetation provides all the nutrients required by the species.

Acoustic monitoring detected manatee vocalisations for months inside the shallow wetlands surrounding the San San and Changuinola rivers, where they are presumed to be feeding (Merchan et al. 2019, 2024; Guzman 2024, unpublished data). A long term acoustic study counted and mapped manatees using side-scan sonar in the San San Pond Sak wetland, for 12 months.  A total of 214 sonar transects, covering 1,731 km and detecting 1,004 manatees were used to generate density and abundance estimates. Animals were most likely to be found in the deeper narrow tributaries or the shallow lagoon near the river mouth. Abundance varied by season.  A Bayesian model, using daily variance in counts, indicated that there were 22–71 animals at peak season, and 1–6 in December (Guzman and Condit, 2017).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

Due to the restricted movement and high residency, the Guiana dolphins are most likely isolated from South America. The closest known population of this species is approximately 600 km to the north, in Cayos Miskitos, Nicaragua. To the south, the population is located in the Gulf of Urabá (more than 660 km away), in the Colombian Caribbean (Caballero et al., 2018). A comparison of whistle repertoire among Guiana dolphins throughout their range suggests that the dolphins between Costa Rica and Panama produce very different whistles than those from 15 populations in South America (May-Collado, in review), supporting the hypothesis of geographical isolation between Central and South America populations occur (May-Collado and Wartzok, 2009; May-Collado, 2010).