West Indian Manatee Trichechus Manatus Research Articles

Home ranges of released West Indian manatees Trichechus manatus in Brazil

AbstractThe distribution of the Vulnerable West Indian manatee Trichechus manatus is influenced by physical and environmental factors such as water salinity, temperature and depth, freshwater supply and the availability of food resources. In Brazil, information on the habitat use of this species is insufficient for effective conservation. Here, we monitored manatees that had been found stranded as calves, rehabilitated in captivity and subsequently released, to identify their home ranges and examine their adaptation to life in the wild. The study, which involved monitoring six manatees using satellite and VHF telemetry systems, was conducted during 2016–2019 in the states of Paraíba, Sergipe and Bahia in north-eastern Brazil. Home range size of individuals was 2.56–42.07 km2 and all fidelity sites (areas used most frequently) were within protected areas. The longest distance travelled from the coastline upriver was 14.24 km and the longest distance offshore was 0.93 km. There were no significant differences in home range data between the dry and rainy seasons, but there was significant difference between the sexes, with males travelling across larger areas than females. All but one of the six individuals met the majority of indicators established in the Brazilian Manatee Reintroduction Protocol, and thus were considered to have successfully adapted to the wild. Our study provides information on patterns of habitat use and areas intensely used by manatees, which can assist protected area managers in defining priority areas for manatee conservation in Brazil.

Molecular confirmation of twinning in the West Indian Manatee (Trichechus manatus)

Abstract: Few twinning events have been recorded in the West Indian manatee (Trichechus manatus, Sirenia: Trichechidae) and no previous published study has provided confirmation of this phenomenon based in molecular tools. Here we investigate a possible case of twinning in an endangered Brazilian population of T. manatus using molecular tools. We analyzed two male neonates found stranded in Ceará State, on the northeastern coast of Brazil. The DNA of both individuals was isolated, and 10 microsatellite loci were amplified and genotyped. Following the identification of the alleles, the probabilities of identity by descent (∆7 and ∆8) and relatedness (rxy) were calculated using estimators that evaluate inbreeding. The two individuals shared most of the alleles, with differences in the genotypes being identified in only two loci. All the estimators identified a level of relatedness compatible with that found between siblings (selfed or outbred), indicating they were dizygotic twins. This is the first confirmed case of fraternal twins in free-ranging West Indian manatees in South America. The recognition of this type of twinning provides elements to improve actions for the rehabilitation of stranded animals and their subsequent release to the environment.

Manual Collection and Semen Characterization in a West Indian Manatee (Trichechus manatus).

Limited information is available regarding male reproductive physiology in West Indian manatees (Trichechus manatus). Currently, only basic ultrastructural and morphometric descriptions of the spermatozoon exist; however, there are no reports evaluating any seminal characteristics in this species. Therefore, the aim of the study was to fill current gaps in knowledge regarding semen parameters in West Indian manatees by collecting and characterizing multiple ejaculate samples from a single, adult West Indian manatee. Samples were analyzed for the following semen parameters: volume, agglutination, pH, osmolality, viscosity, concentration, total sperm number, motility and kinematic parameters, morphology, plasma membrane integrity, acrosome integrity, chromatin maturation, and chromatin condensation. All macroscopic semen parameters varied to some extent between samples. Total and progressive motility was high for ejaculates 2 to 5, exceeding 97 and 89%, respectively; however, these parameters decreased dramatically throughout ejaculates 6 and 7. Across all samples, curvilinear velocity, straight-line velocity, and average pathway velocity represented the largest significant differences (p < 0.001) between each of the progression velocity subgroups (rapid, medium, slow). Sperm characteristics, including acrosome integrity (79.8%), chromatin condensation (93.1%), and chromatin maturation (99.5%) were very high; however, high numbers of morphologically abnormal sperm were present (52.9%) and plasma membrane integrity was low (45.1%). These results are the first of their kind for this species and suggest high semen quality, based on multiple ejaculates, in this male West Indian manatee.

Internal parasites of the two subspecies of the West Indian manatee Trichechus manatus

The West Indian manatee Trichechus manatus is divided into 2 subspecies: the Antillean (T. m. manatus) and Florida (T. m. latirostris) manatees. This study reports sample prevalence of manatee parasites from populations of these 2 subspecies in different geographical locations. Although necropsy is a valuable diagnostic tool for parasite infections, the need for antemortem diagnostic techniques is important. Fecal samples collected during necropsies of Antillean manatees (n = 3) in Puerto Rico and Florida manatees (n = 10) in Crystal River, Florida, as well as from live-captured Florida manatees (n = 11) were evaluated using centrifugal flotation with sucrose and ethyl acetate sedimentation to compare parasites from each of the populations. Although both fecal examination methods provided similar results, the centrifugal flotation method required less time for diagnosis. The most common parasite eggs found in both populations included the trematodes Pulmonicola cochleotrema and Nudacotyle undicola, oocysts of the coccidian Eimeria spp., and eggs of the ascarid Heterocheilus tunicatus. Eggs of the trematode Chiorchis groschafti were found in both populations of manatees; however, eggs of a related species, Chiorchis fabaceus, were abundant in the Florida samples, but not found in Puerto Rico populations. Trematode eggs of Moniligerum blairi were found in both populations, but were more common in the Florida manatee (42%) than the Antillean manatee (33%). To our knowledge, this is the first report of both Eimeria manatus and Eimeria nodulosa oocysts in Antillean manatees from Puerto Rico.

Sighting demographics of the West Indian manatee Trichechus manatus in the north-central Gulf of Mexico supported by citizen-sourced data

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 32:321-332 (2017) - DOI: https://doi.org/10.3354/esr00817 Sighting demographics of the West Indian manatee Trichechus manatus in the north-central Gulf of Mexico supported by citizen-sourced data Elizabeth E. Hieb1,*, Ruth H. Carmichael1,2, Allen Aven1,2, Courtney Nelson-Seely1, Nicole Taylor1 1Dauphin Island Sea Lab, Dauphin Island, Alabama 36528, USA 2University of South Alabama, Mobile, Alabama 36688, USA *Corresponding author: ehieb@disl.org ABSTRACT: Traditional research methods are often limited in their ability to capture broad spatial and temporal changes in species distribution that affect global patterns of biodiversity. To provide range-wide demographic data needed to quantify and evaluate changes in habitat use and support ongoing recovery efforts for the endangered West Indian manatee Trichechus manatus, we analyzed data from a formal manatee sighting network that uses citizen-sourced data for the understudied north-central Gulf of Mexico region. Although historically considered to be outside manatees’ typical US range, more than 1700 opportunistic, publicly reported manatee sightings and 23 mortalities have been documented in Alabama and Mississippi since the early 1900s. Live manatee sightings have occurred primarily during warmer months in rivers and subembayments. Manatee mortalities have significantly increased since the mid-1980s and have most often been attributed to cold stress, with 2 known mortalities due to vessel strikes in recent years. Sightings of individual manatees were most common, but group sizes of up to 17 were reported, typically in late summer. Decadal-scale trends in opportunistic sighting records demonstrate persistent spatial and temporal patterns of manatee occurrence in the north-central Gulf of Mexico and suggest greater use and importance of the region as seasonal manatee habitat than previously documented. If applied appropriately, citizen-sourced data have the potential to enhance targeted research efforts, significantly contribute to ecological datasets for a number of species, and provide a useful tool to enhance conservation and management. KEY WORDS: Manatee · Gulf of Mexico · Distribution · Citizen science · Opportunistic data Full text in pdf format Supplementary material PreviousNextCite this article as: Hieb EE, Carmichael RH, Aven A, Nelson‑Seely C, Taylor N (2017) Sighting demographics of the West Indian manatee Trichechus manatus in the north-central Gulf of Mexico supported by citizen-sourced data. Endang Species Res 32:321-332. https://doi.org/10.3354/esr00817 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 32. Online publication date: April 07, 2017 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2017 Inter-Research.

Spatial and temporal distribution of manatees (trichechus manatus) reintroduced in the northeastern coast of Brazil

Many West Indian manatees (Trichechus manatus) that strand along the northeast Brazilian coast are calves, which are often rescued and carried to the Peixe-Boi Project rehabilitation facilities in Itamaracá, Pernambuco State where they are prepared to reintroduction. During the ten years period of October 1994 to December 2004, thirteen captive manatees were radio tagged, released and tracked in three main northeast coastal areas as part of the Brazilian Manatee Reintroduction Program. All individuals were monitored locally with VHF transmitters, during brief periods, four were also tracked remotely with satellite-monitored radio tags. Five manatees (39.5%) had long-term tracks over 14 months or 420 days (Total= 10166 days; Maximum=2663 days; Mean=2031 days; SD=1572 days) that met criteria for inclusion in analyses of spatial and seasonal movement patterns. Manatees were tracked from Praia do Forte, Bahia (12.538ºS/38.474ºW) to Macau, Rio Grande do Norte (5.084ºS/36.682ºW), covering around 1200 km and six states along the northeast coast. Three manatees occupied large home ranges, with each containing a few sites of high fidelity where they spent considerable time, while two used restrict home range having only one site with high fidelity. Others two manatees not showed movements along coast and occupied a restrict area like their fidelity site. Two manatees with short tracking histories showed visible weight loss soon after release and were re-captured after having moved long distances, including offshore movements into deep waters. The high rate of survival for released manatees, their adaptation to areas within the former range of wild manatees, and birth of a calf to a released captive manatee are indicators of the success of the Brazilian Manatee Reintroduction Program.

Contaminant concentrations, biochemical and hematological biomarkers in blood of West Indian manatees Trichechus manatus from Brazil

The West Indian manatee Trichechus manatus is threatened with extinction in Brazil, and this study focused on nondestructive blood samples analyzed for metals, polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), as well as biochemical and hematological biomarkers. Studied manatees were kept at Projeto Peixe-Boi headquarters in Pernambuco State, and at two natural areas in estuaries where they are released to the wild. Manatees kept at the natural estuary in Paraiba State have blood concentrations of Al, Pb, Cd, Sn that are 11, 7, 8 and 23 times greater, respectively, than the concentrations found in blood of animals from the same species in Florida, USA. An inhibition of butyrylcholinesterase in manatees kept at the two reintroduction sites in Alagoas and Paraiba States indicated possible exposure of the animals to cholinesterase inhibitor insecticides. PCBs and OCPs were not detected. Results from this study will help delineate conservation efforts in the region.

Low genetic variation and evidence of limited dispersal in the regionally important Belize manatee

AbstractThe Antillean subspecies of the West Indian manatee Trichechus manatus is found throughout Central and South America and the Caribbean. Because of severe hunting pressure during the 17th through 19th centuries, only small populations of the once widespread aquatic mammal remain. Fortunately, protections in Belize reduced hunting in the 1930s and allowed the country's manatee population to become the largest breeding population in the Wider Caribbean. However, increasing and emerging anthropogenic threats such as coastal development, pollution, watercraft collision and net entanglement represent challenges to this ecologically important population. To inform conservation and management decisions, a comprehensive molecular investigation of the genetic diversity, relatedness and population structure of the Belize manatee population was conducted using mitochondrial and microsatellite DNA. Compared with other mammal populations, a low degree of genetic diversity was detected (HE=0.455; NA=3.4), corresponding to the small population size and long‐term exploitation. Manatees from the Belize City Cayes and Southern Lagoon system were genetically different, with microsatellite and mitochondrial FST values of 0.029 and 0.078, respectively (P≤0.05). This, along with the distinct habitats and threats, indicates that separate protection of these two groups would best preserve the region's diversity. The Belize population and Florida subspecies appear to be unrelated with microsatellite and mitochondrial FST values of 0.141 and 0.63, respectively (P≤0.001), supporting the subspecies designations and suggesting low vagility throughout the northern Caribbean habitat. Further monitoring and protection may allow an increase in the Belize manatee genetic diversity and population size. A large and expanding Belize population could potentially assist in the recovery of other threatened or functionally extinct Central American Antillean manatee populations.

Feeding preferences of West Indian manatees in Florida, Belize, and Puerto Rico as indicated by stable isotope analysis

The endangered West Indian manatee Trichechus manatus has 2 recognized sub- species: the Florida T. m. latirostris and Antillean T. m. manatus manatee, both of which are found in freshwater, estuarine, and marine habitats. A better understanding of manatee feeding preferences and habitat use is essential to establish criteria on which conservation plans can be based. Skin from manatees in Florida, Belize, and Puerto Rico, as well as aquatic vegetation from their presumed diet, were analyzed for stable carbon and nitrogen isotope ratios. This is the first application of stable iso- tope analysis to Antillean manatees. Stable isotope ratios for aquatic vegetation differed by plant type (freshwater, estuarine, and marine), collection location, and in one instance, season. Carbon and nitrogen isotope ratios for manatee skin differed between collection location and in one instance, sea- son, but did not differ between sex or age class. Signatures in the skin of manatees sampled in Belize and Puerto Rico indicated a diet composed primarily of seagrasses, whereas those of Florida mana- tees exhibited greater regional variation. Mixing model results indicated that manatees sampled from Crystal River and Homosassa Springs (Florida, USA) ate primarily freshwater vegetation, whereas manatees sampled from Big Bend Power Plant, Ten Thousand Islands, and Warm Mineral Springs (Florida) fed primarily on seagrasses. Possible diet-tissue discrimination values for 15 N were estimated to range from 1.0 to 1.5‰. Stable isotope analysis can be used to interpret manatee feed- ing behavior over a long period of time, specifically the use of freshwater vegetation versus sea- grasses, and can aid in identifying critical habitats and improving conservation efforts.

Comments on “Intraspecific and geographic variation of West Indian manatee (Trichechus manatus spp.) vocalizations” [J. Acoust. Soc. Am. 114, 66–69 (2003)

This letter concerns the paper "Intraspecific and geographic variation of West Indian manatee (Trichechus manatus spp.) vocalizations" [Nowacek et al., J. Acoust. Soc. Am. 114, 66-69 (2003)]. The purpose here is to correct the fundamental frequency range and information on intraindividual variation in the vocalizations of Amazonian manatees reported by Nowacek et al. (2003) in citing the paper "Signature information and individual recognition in the isolation calls of Amazonian manatees, Trichechus inunguis (Mammalia: Sirenia)" [Sousa-Lima et al., Anim. Behav. 63, 301-310 (2002)].

Background noise reduction of manatee vocalizations

The West Indian manatee (Trichechus manatus latirostris) has become an endangered species in the United States partly because of an increase in the number of collisions with boats. A device to alert boaters of the presence of manatees is desired. Previous research has shown that background noise limits the detection range (which is critical for practical implementation). By improving the signal-to-noise ratio of the vocalization signal, it is possible to extend the detection range. The finite impulse response (FIR) structure of the adaptive line enhancer (ALE) can detect and track narrow-band signals buried in broadband noise. In this paper, a constrained infinite impulse response (IIR) ALE, called a feedback ALE (FALE), is implemented to reduce the background noise. In addition, a bandpass filter is used as a baseline for comparison. A library consisting of 100 manatee calls spanning ten different signal categories is used to evaluate the performance of the bandpass filter, FIR-ALE, and FALE. The results show that the FALE is capable of reducing background noise by about 6.0 and 21.4 dB better than that of the FIR-ALE and bandpass filter, respectively, when the signal-to-noise ratio (SNR) of the original manatee call is −5 dB.

Development of predictive models to explain the distribution of the West Indian manatee Trichechus manatus in tropical watercourses

Logistic regressions were used to study the relationship between habitat variables and the use of tropical watercourses by the West Indian manatee Trichechus manatus at Northeastern Costa Rica and Southern Nicaragua. Presence of manatees in watercourses was assessed through direct and reported sightings of individuals and feeding signs on aquatic vegetation. Indirect methods provided good approximations to the actual distribution that could not have been achieved through direct observations or aerial surveys. Best multivariate models showed that manatees were most present in watercourses that presented abundant aquatic vegetation, warm, and clear waters, high forest cover, and are wider than those where the species is absent. Although habitat variables that explain habitat use of manatees differed for the two sectors found within the study area, manatees preferred lagoons to other watercourses in both areas. These findings point to forest clearing on the shores as a threat for manatee conservation. Habitat variables are excellent predictors of manatee presence, and predictive models as those developed in this study can help assess potential distribution of manatees in areas where this information is lacking as well as to assist identify potential reintroduction areas.

Phylogeography and population genetics of the endangered Amazonian manatee, Trichechus inunguis Natterer, 1883 (Mammalia, Sirenia)

We used mitochondrial DNA control region sequences to examine phylogeography and population differentiation of the endangered Amazonian manatee Trichechus inunguis. We observe lack of molecular differentiation among localities and we find weak association between geographical and genetic distances. However, nested clade analysis supports restricted gene flow and/or dispersal with some long-distance dispersal. Although this species has a history of extensive hunting, genetic diversity and effective population sizes are relatively high when compared to the West Indian manatee Trichechus manatus. Patterns of mtDNA haplotype diversity in T. inunguis suggest a genetic disequilibrium most likely explained by demographic expansion resulting from secession of hunting and enforcement of conservation and protective measures. Phylogenetic analysis of T. manatus and T. inunguis haplotypes suggests that T. inunguis is nested within T. manatus, effectively making T. manatus a paraphyletic entity. Paraphyly of T. manatus and recent divergence times of T. inunguis and the three main T. manatus lineages suggest a possible need for a taxonomic re-evaluation of the western Atlantic Trichechus.

Echeneid–sirenian associations, with information on sharksucker diet

Association of the sharksucker Echeneis naucrates and whitefin sharksucker E. neucratoides with the West Indian manatee Trichechus manatus and the dugong Dugong dugon is presented and discussed. Alimentary tract‐content analysis and field observations suggest that coprophagy (feeding on host faecal material) may be the primary food source for echeneids associated with sirenian hosts.

Distribution, habitat, and conservation status of the West Indian manatee Trichechus manatus in French Guiana

Interview surveys of 116 coastal residents and fishermen and surveys by motorboat were conducted in 2000 and 2001 in French Guiana in order to assess the distribution, habitats and conservation status of the West Indian manatee Trichechus manatus. There were 72 reported sightings of manatees, and we made 10 sightings during river surveys. Interviews suggested that manatees may be less abundant than in the recent past, but are still present and regularly sighted all along the coast and in estuaries up to 80 km inland. The main reason for any recent decline is probably hunting for meat, pressures from development and, in some areas, pollution from maritime traffic. Although only opportunistically caught, manatees are still poached. In some areas they are killed for cultural beliefs, but only on a small scale. The main habitat for the manatee in French Guiana is estuarine mangroves. A survey at Coswine, an area where manatees have been sighted year-round, indicated that this mangrove area is characterized by biotic and abiotic factors within the range known to provide suitable habitat for the species. However, habitats for manatees in French Guiana are limited and receive little formal protection, and the species' status is based more on fortuitous protection than on any active conservation. Public awareness programmes for the manatee are currently being developed by local NGOs, but a regional conservation programme is also required.

Heavy poaching in prime habitat: the conservation status of the West Indian manatee in Nicaragua

This study provides an overview of the conservation status of the West Indian manatee Trichechus manatus in Nicaragua, including data on habitat availability, manatee distribution and relative abundance, and current threats. The data is based on surveys from boats and extensive interviews with local people. Nicaragua harbors one of the largest areas of habitat suitable for manatees in Central America. The species has an almost continuous distribution along the country's eastern, Caribbean coast and inland in some watercourses. There are larger groups of manatees in brackish lagoons than in freshwater rivers. Seasonal migrations and lengthy daily travels influenced by tides have been reported. The main threats to these manatees include poaching and incidental drowning in fishing nets, while boat traffic, pollution and habitat loss presently seem to be negligible factors in Nicaragua. Poaching is widespread along the coast and it is estimated that c. 40 manatees are killed annually throughout the country. Enforcement of hunting laws and protected areas is almost non-existent, with the exception of the Southeastern Nicaragua Biosphere Reserve. This may explain why manatees have disappeared from a few areas and become rare in others. Unless restrictions are imposed on poaching and on the use of gill nets within inland wetlands, the West Indian manatee may become rare throughout Nicaragua in the near future.

Translocation of Blue and Gold Macaw Ara ararauna into its historical range on Trinidad

New World parrots are declining throughout their range. Blue and Gold Macaw Ara ararauna was extirpated from the island of Trinidad in the late 1960s through anthropogenic processes. The Cincinnati Zoo & Botanical Garden is assisting the Wildlife Section of the Forestry Division, Trinidad on a mission to restore the species into its historical range within the Bush-Bush Sanctuary in the Nariva Swamp. The Sanctuary has been protected by the government of Trinidad and is the home of the endangered Red-bellied Macaw Ara manilata and West Indian Manatee Trichechus manatus. Zoo and Wildlife personnel participated in three separate releases, beginning in December 1999 through to March 2000. The initial release consisted of an identical sex group of macaws followed by two additional releases of pairs/groups of birds. Of 18 Blue and Gold Macaws, 14 were released into the Nariva Swamp and are currently being monitored by the Wildlife Section, Zoo personnel and surrounding community. Translocation of wild populations of parrots has proven to be a viable solution to restocking wild populations that have been regionally extirpated.

Characterizing Manatee habitat use and seagrass grazing in Florida and Puerto Rico: implications for conservation and management

The Indian River Lagoon on the Atlantic coast of Florida, USA, and the east coast of Puerto Rico provide contrasting environments in which the endangered West Indian Manatee Trichechus manatus experiences different thermal regimes and seagrass communities. We compare Manatee feeding behaviour in these two regions, examine the ecological effects of Manatee grazing on a seagrass community in the Indian River Lagoon, describe the utility of aerial surveys, radio tracking, and seagrass mapping to study Manatee feeding patterns, and develop hypotheses on sirenian feeding strategies in temperate and tropical seagrass communities. In both the Indian River Lagoon and Puerto Rico, Manatees were typically observed grazing in water depths = 2.0 m and more frequently on the most abundant seagrasses present in the community: Halodule wrightii in the Indian River Lagoon and Thalassia testudinum in eastern Puerto Rico. Where both H. wrightii and Syringodium filiforme were consumed in the Indian River Lagoon, Manatees tended to remove more S. filiforme than H. wrightii rhizome + root biomass. Even though 80 to 95% of the short-shoot biomass and 50 to 67% of the rhizome + root biomass were removed, grazed patches of H. wrightii and S. filiforme recovered significantly between February and August. H. wrightii may be both more resistant and resilient than S. filiforme to the impacts of Manatee grazing. Despite the significantly greater abundance of T. testudinum in Puerto Rico, Manatees exhibited selective feeding by returning to specific sites with abundant H. wrightii. They also appeared to feed selectively on T. testudinum shoots associated with clumps of the calcareous alga Halimeda opuntia. We hypothesize that Florida Manatees are less specialized seagrass grazers than Manatees in tropical regions like Puerto Rico. Continued research on Manatee grazing ecology in temperate to tropical seagrass communities will enable better protection and management of these vital and unique marine resources.

Recent observations and records of the West Indian manatee Trichechus manatus in northeastern Brazil

Sixteen boat surveys and observations from reefs were conducted between January and May 1986 in the region of Barra de Mamanguape, Paraíba, Brazil, to assess the occurrence of West Indian manatees Trichechus manatus. Sightings of one to three individuals were made on eleven occassions in inshore waters protected by reefs and at the offshore sides of reefs. Manatees were only observed in March and April. Possible movements between sea and inshore waters could incidate a need for freshwater and/or be related to foraging preferences and migration. Direct threats to manatee survival in the state of Paraíba include hunting and accidental catches. Degradation of suitable habitat might also increase manatee vulnerability in Barra de Mamanguape. Recent records suggest existing remnant populations of unknown size in northeastern Brazil, which should receive further attention and implementation of conservation measures.

The use of manatees for the control of aquatic weeds in Guyana

The West Indian Manatee (Trichechus manatus) has been widely suggested as a means of biological control of aquatic weeds. Despite significant research little data is available from existing manatee installations.