How to detect an elusive aquatic mammal in complex environments? A study of the Endangered Antillean manatee Trichechus manatus manatus in French Guiana

Analysis of body condition indices reveals different ecotypes of the Antillean manatee

Assessing the body condition of wild animals is necessary to monitor the health of the population and is critical to defining a framework for conservation actions. Body condition indices (BCIs) are a non-invasive and relatively simple means to assess the health of individual animals, useful for addressing a wide variety of ecological, behavioral, and management questions. The Antillean manatee (Trichechus manatus manatus) is an endangered subspecies of the West Indian manatee, facing a wide variety of threats from mostly human-related origins. Our objective was to define specific BCIs for the subspecies that, coupled with additional health, genetic and demographic information, can be valuable to guide management decisions. Biometric measurements of 380 wild Antillean manatees captured in seven different locations within their range of distribution were obtained. From this information, we developed three BCIs (BCI₁ = UG/SL, BCI₂ = W/SL³, BCI₃ = W/(SL*UG²)). Linear models and two-way ANCOVA tests showed significant differences of the BCIs among sexes and locations. Although our three BCIs are suitable for Antillean manatees, BCI₁ is more practical as it does not require information about weight, which can be a metric logistically difficult to collect under particular circumstances. BCI₁ was significantly different among environments, revealing that the phenotypic plasticity of the subspecies have originated at least two ecotypes-coastal marine and riverine-of Antillean manatees.

Occupancy and population density estimates of the Amazonian manatee in eastern Ecuador

The Amazonian manatee Trichechus inunguis has been categorized as Vulnerable by the IUCN. There have been few studies on the species in its natural habitats due to its elusive nature and the low visibility of its aquatic habitats. Understanding the conservation status of Amazonian manatees, as well as any changes in their population trends and direct threats, is the basis for their management and conservation. Our study was carried out in 2 localities of the Ecuadorian Amazon (Tambococha-Jatuncocha and the Lagarto River), in the provinces of Sucumbíos and Orellana. We surveyed Amazonian manatees along rivers and in lagoons, using fish finder side-scan sonar to increase detectability rates. We estimated encounter rates, population density and occupancy. With a sampling effort of 573 km, we obtained an average encounter rate of 0.90 records 10 km-1 and estimated a population density of 1.09 and 0.94 ind. km-2 in Tambococha-Jatuncocha and the Lagarto River, respectively. In addition, occupancy rates varied between 0.51 and 0.57, and presence and distribution of the species were associated with distance to humans. The Amazonian manatee population estimates presented here represent a baseline for future research, and additional surveys will be needed to understand population fluctuations over time. An evaluation of population viability in Tambococha-Jatuncocha and the Lagarto River would also be required to determine whether these populations will be able to persist over the long term under different deterministic and stochastic scenarios.

Applications of eDNA Metabarcoding for Vertebrate Diversity Studies in Northern Colombian Water Bodies

Environmental DNA metabarcoding is a tool with increasing use worldwide. The uses of such technology have been validated several times for diversity census, invasive species detection, and endangered/cryptic/elusive species detection and monitoring. With the help of this technology, water samples collected (n = 37) from several main river basins and other water bodies of the northern part of Colombia, including the Magdalena, Sinú, Atrato, and San Jorge river basins, were filtered and analyzed and processed using universal 12S primers for vertebrate fauna and NGS. Over 200 native taxa were detected, the majority of them being fish species but also including amphibia, reptiles, and several non-aquatic species of birds and mammals (around 78, 3, 2, 9, and 8%, respectively). Among the matches, vulnerable, and endangered species such as the catfish Pseudoplatystoma magdaleniatum and the Antillean manatee (Trichechus manatus) were detected. The manual revision of the data revealed some geographical incongruencies in classification. No invasive species were detected in the filters. This is, to our knowledge, the first time this technique is used in rivers of the country and this tool promises to bring advances in monitoring and conservation efforts, since its low cost and fast deployment allows for sampling in small periods of time, together with the fact that it can detect a wide range of species, allows for a new way of censing the vertebrate diversity in Colombia. Diversity analysis showed how the species identified using this method point to expected community structure although still much needs to be improved in rates of detection and genomic reference databases. This technique could be used in citizen science projects involving local communities in these regions.

The presence of ovarian cysts in a captive Antillean manatee (Trichechus manatus manatus L. 1758)

Background

Several pathological changes associated with reproductive systems of marine mammals have been reported in primary literature. However, no such records exist regarding ovarian cysts in the Antillean manatee (Trichechus manatus manatus L. 1758).

Case presentation

A nulliparous female Antillean manatee, held in captivity at the Wroclaw Zoological Garden, died in April 2015. The animal was 370 cm long from nose to tail and weighed 670 kg. The width of manatee’s fluke was 80 cm. The post-mortem examination of the reproductive system showed the numerous pathological cysts on the external surface of the left and the right ovaries. Morphologically, the cysts had varying diameters and were attached to the ovaries by stalks. Some of the cysts were thin-walled and contained fluid, while several others were solid or contained a semi-solid mass. The structure of the ovaries displayed features of the polycystic ovary syndrome (PCOS). The cysts also exhibited positivity with cytokeratin and vimentin. There were no pathological changes within the uterus, uterine tube and vagina.

Conclusion

Although we were unable to definitively determine the exact source of the ovarian cysts in the studied manatee, we found that one of the causes may be age-related. Our study also revealed that ovarian cysts in the Antillean manatee form both types of corpora lutea (CL).

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1164-7) contains supplementary material, which is available to authorized users.