Wild Manatees Research Articles

Accomplishments and challenges of the research on Antillean manatee: A bibliometric analysis

The Antillean manatee (Trichechus manatus manatus) is an endangered subspecies of the West Indian manatee inhabiting countries of South America, Meso America and the Caribbean. Basic and applied research is necessary to inform management plans for the effective recovery of this subspecies. The purpose of this study was to systematically review literature regarding Antillean manatees, without restriction of the research topic. Article selection and screening process are described. Our final database consisted of 456 publications, of which peer-reviewed literature (articles, reviews, and notes in research journals) represent the most important type (63.4%), followed by BSc, MSc, and PhD theses (28.1%). Most of the research (70%) was conducted on wild manatees, 21,5% under human care conditions, and the rest a combination of both; the most common topics of study were ‘ecology’, ‘conservation’, ‘morphology, anatomy and physiology’, and ‘behavior’. The literature on Antillean manatee has expanded significantly over the last two decades across the region, with most of the research published in just the last five (25.4%) to 10 (44.6%) years. Most of the published work has been by Brazilian, Mexican, and Colombian researchers. However, an important amount of research remains as theses in Portuguese or Spanish limiting the dissemination of results. Relevant limitations for research and publication in Latin American countries may have an impact on the published literature on Antillean manatees, including scarce funding, poor facilities, language-related difficulties, and lack of a culture of publication. Avenues to melt scientific barriers may include increasing governmental investment on research, strengthening international networks, and improving the support to publish in high-impact journals.

The Antillean manatee produces broadband vocalizations with ultrasonic frequencies

Antillean manatees produce vocalizations reported to be important for communication, but their vocal behavior throughout their geographic range is poorly understood. A SoundTrap recorder (sample rates: 288/576 kHz) was deployed in Belize to record vocalizations of wild manatees in a seagrass channel and of a young rehabilitated and released manatee in a shallow lagoon. Spectral analysis revealed broadband vocalizations with frequencies up to 150 kHz and a high proportion of calls with ultrasonic components. Ultrasonic frequency components appear prevalent in their vocal repertoire and may be important to manatee communication.

Serum proteins in healthy and diseased Florida manatees (Trichechus manatus latirostris)

A major goal of this study was to determine whether serum protein fractions of healthy Florida manatees differ with age, sex, or living environments (wild versus housed). A second goal was to determine which serum protein fractions vary in diseased versus healthy manatees. Serum protein fractions were determined using agarose gel electrophoresis. Healthy adults had slightly higher total serum protein and total globulin concentrations than younger animals. This largely resulted from an increase in gamma globulins with age. Total serum protein, albumin, alpha-1 globulin, beta globulin, and total globulin concentrations were slightly higher in housed manatees compared to wild manatees, but there was no significant difference in the albumin/globulin (A/G) ratio, suggesting a difference in hydration between these groups. No significant differences were attributable to sex or pregnancy. Serum albumin concentrations and A/G ratios were significantly lower for manatees with boat trauma, entanglements, emaciation, or cold stress compared to healthy manatees. Variable increases were seen in alpha-1globulins, alpha-2 globulins, beta globulins, and gamma globulins. These globulin fractions contain positive acute-phase proteins and immunoglobulins, and their increases may reflect acute or chronic active inflammation. Changes in serum protein fractions were not consistent enough to justify the use of serum protein electrophoresis as a routine diagnostic test for manatees. However, serum (or plasma) protein electrophoresis is required when accurate values for albumin and globulins are needed in manatees and in determining which protein fractions may account for a hyperproteinemia or hypoproteinemia reported in a clinical chemistry panel.

Thromboelastography in wild Florida manatees (Trichechus manatus latirostris).

Thromboelastography (TEG) provides a comprehensive evaluation of blood clot formation. This test can be used to identify abnormalities in coagulation by assessing multiple aspects of the clotting cascade, including the speed of clot initiation and formation, clot strength, and ultimately fibrinolysis. Thromboembolic disease has been hypothesized to play a role in the pathophysiology of cold stress syndrome (CSS), an important cause of mortality in the threatened Florida manatee (Trichechus manatus latirostris). The objective of this study was to establish thromboelastography RIs using the TEG 5000 with citrated whole blood samples and kaolin activation in wild, healthy manatees. In December 2014 and January 2015, 29 wild manatees (17 male and 12 female) were blood sampled as part of the annual wild manatee health assessments organized by United States Geological Survey (USGS). TEG was performed using citrated kaolin-activated samples. The samples were obtained from manatees caught in Crystal River, Citrus County, and used to identify the mean±SD of normal TEG parameters: R=reaction time 2.1minutes (0.8), K=clot formation time 0.8min (0), α angle=83.1° (2), MA=maximum amplitude 75mm (7.6), and LY30=clot lysis 0.41% (0.68). No significant differences were found between manatee size, sex, or time between sampling and running the test. Manatee TEG parameters demonstrate a relatively hypercoagulable condition when compared to other mammals. This information will facilitate detection of changes in hemostasis during injury and disease and provide a valuable reference range.

Environmentally friendly parametric alarm for alerting marine mammals of approaching vessels

Marine mammals are vulnerable to boat, barge, and ship collisions. Although more commonly identified and reported in busy coastal areas, collisions are not restricted to shipping lanes or shallow water environments. A common denominator is that they all occur near the surface. Here the acoustical laws of reflection and propagation significantly limit the ability of marine mammals to hear and locate the sounds of approaching vessels. Acoustic measurements from controlled ship passages through vertical hydrophone arrays demonstrate the confluence of factors that poses auditory detection challenges for both whales and manatees. A highly directional, environmentally-friendly, low intensity underwater parametric alarm has been developed to mitigate these challenges & safely alert marine mammals of approaching vessels. The efficacy has been demonstrated with wild manatees. Ninety-five percent of manatees during alarm-on trials elicited avoidance reactions while only 5% of manatees during alarm-off trials elicit...

Bottlenecks in the migration routes of Amazonian manatees and the threat of hydroelectric dams

ABSTRACT In a particular region within western Amazonia, Amazonian manatees (Trichechus inunguis) live in a floodplain environment that becomes inhospitable for them during the annual low-water season. To flee from it, they undergo a dangerous migration to a refuge while water levels are dropping fast. Our aim was to better understand the role of depth variation in this migratory process. We analyzed the sole tracking data on wild manatees (n=10 males), 30 years of Landsat images, a 14-year hydrograph and a 3-D bathymetric model. Migratory routes contained shallower segments, here called 'migratory bottlenecks', which dried out at the end of most lowering-water seasons, blocking the passage to the refuge. Manatees began migrating just in time to traverse the bottlenecks furthest away, suggesting they fine-tuned their departure so as to maximize time within the foraging home range without compromising safety. They apparently achieved this by estimating depth at the bottlenecks. Moreover, a bottleneck was created in >15 years, illustrating the environment's dynamism and the challenge this imposes upon manatees. Our results are probably generalizable to most of the species' range. We contend manatees possess an updatable cognitive map of their environment and are behaviorally plastic. Current dam-building plans, if implemented, would create more bottlenecks and make flooding less predictable, increasing manatee mortality from unsuccessful migrations. It would also partition the species into small populations, each prone to short-term extinction. The natural outcome would be the second species-level collapse. Economic growth should not come at the expense of the extinction of the iconic manatee.

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

AbstractThe Antillean manateeTrichechus manatus manatusis a cryptic mammal that inhabits, among other areas, murky rivers and estuaries of Central and South America. The difficulty in detecting and counting manatees is an obstacle to monitoring their population status, as traditional count sampling is unsuitable. We conducted a quantitative analysis of the distribution and abundance of the manatee across its known range in the rivers and estuaries of French Guiana, based on data from a range-wide line transect visual survey combined with a side-scan sonar survey, identification of feeding sites, and silent observations at fixed points. A total effective effort of 248 hours and 1,129 km of boat survey was completed. We used two relative abundance indices: the combined encounter rate, which combines encounters per km from either visual or side-scan sonar surveys, and the global detection index, which is defined as the sum of all evidence per unit time. Manatees were detected in all nine study units. Niche modelling was used to analyse the space selection by manatees, and helped to detect differential use of habitats according to the season. The model predicted that coastal areas are used more extensively during the dry season. In the absence of better techniques to detect wild manatees in complex habitats this monitoring protocol may be relevant and replicable in hydrological systems where manatee detectability is constrained by biogeographical characteristics.

New parametric acoustic alarm proves effective at alerting wild manatees of approaching boats

The efficacy of a bow mounted parametric acoustic alarm for alerting manatees of approaching boats was demonstrated with wild manatees in Florida. Two experimental conditions were tested; (1) boat approaches with the alarm-on, and (2) approaches with the alarm-off. Synchronized underwater acoustic buoys and aerial video recorders documented manatee behavior and acoustic conditions prior to, during, and after controlled boat approaches. 95% of the manatees during alarm-on trials elicited overt changes in behavior (avoidance reactions) prior to the boat reaching the focal manatee. In contrast, only 5% of manatees during alarm-off trials elicited any change in behavior prior to the vessel having to veer off. Changes in behavior observed prior to the boat reaching focal manatees was significantly greater (F = 471.9, df = 1, p< 0.01) during alarm-on trials. The mean distance at which manatees reacted to boat approaches during alarm-on trials was also 20 m compared to only 6m for alarm-off trials (F= 218.4 df =...

Behavioral Lateralization in the Florida Manatee (Trichechus manatus latirostris)

We examined side preferences in the Florida manatee (Trichechus manatus latirostris) through observations of limb use (right and left flipper) in 123 wild and 16 captive individuals. We also analyzed archival data on wild manatees to develop an index of boat-caused body scars to determine lateralization of evasive action. Wild and captive manatees displayed flipper lateralization at the individual, but not the population level for several behaviors including substrate touches, sculling, and feeding. In contrast, manatees were lateralized at the population level for boat-scar biases with more manatees showing a left scar bias (45%) versus right (34%) or dorsal (21%).

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.

Variation in the hindgut microbial communities of the Florida manatee,Trichechus manatus latirostrisover winter in Crystal River, Florida

The Florida manatee, Trichechus manatus latirostris, is a hindgut-fermenting herbivore. In winter, manatees migrate to warm water overwintering sites where they undergo dietary shifts and may suffer from cold-induced stress. Given these seasonally induced changes in diet, the present study aimed to examine variation in the hindgut bacterial communities of wild manatees overwintering at Crystal River, west Florida. Faeces were sampled from 36 manatees of known sex and body size in early winter when manatees were newly arrived and then in mid-winter and late winter when diet had probably changed and environmental stress may have increased. Concentrations of faecal cortisol metabolite, an indicator of a stress response, were measured by enzyme immunoassay. Using 454-pyrosequencing, 2027 bacterial operational taxonomic units were identified in manatee faeces following amplicon pyrosequencing of the 16S rRNA gene V3/V4 region. Classified sequences were assigned to eight previously described bacterial phyla; only 0.36% of sequences could not be classified to phylum level. Five core phyla were identified in all samples. The majority (96.8%) of sequences were classified as Firmicutes (77.3 ± 11.1% of total sequences) or Bacteroidetes (19.5 ± 10.6%). Alpha-diversity measures trended towards higher diversity of hindgut microbiota in manatees in mid-winter compared to early and late winter. Beta-diversity measures, analysed through PERMANOVA, also indicated significant differences in bacterial communities based on the season.

Diagnostic Stages of the Parasites of the Florida Manatee,Trichechus manatus latirostris

Limited information is available on diagnostic stages of parasites in Florida manatees (Trichechus manatus latirostris). We examined 67 fecal samples from captive and wild manatees to define the diagnostic stages of the parasite fauna known to occur in Florida manatees. Parasite eggs were freshly extracted ex utero from identified mature helminths and subsequently characterized, illustrated, and matched to those isolated from fecal samples. In addition, coccidian oocysts in the fecal samples were identified. These diagnostic stages included eggs from 5 species of trematodes (Chiorchis fabaceus, Chiorchis groschafti, Pulmonicola cochleotrema, Moniligerum blairi, and Nudacotyle undicola), 1 nematode (Heterocheilus tunicatus), and oocysts of 2 coccidians (Eimeria manatus and Eimeria nodulosa).

Acoustic tagging for counting feeding events of captive Amazonian manatees

The Amazonian manatee is one of four extant species in the mammalian order Sirenia. They are restricted to the freshwater rivers, lakes and floodplains of the Amazonian river basin where they eat floating and emergent aquatic plants. Visual observation of wild manatees is nearly impossible because of the turbid water and tiny exposure of nose at gentle respiration movement, which consequently precludes study of their underwater behaviour. In this study, we applied animal-worn sound recorder (AUSOMS-mini, System Intec Co., Tokyo, Japan) to two captive Amazonian manatees at INPA, Brazil, in order to record their mastication sounds. Five species of aquatic plants were offered to the manatees separately. Mastication-sounds were extracted by custom made software developed on Matlab for off-line analysis. The mastication intervals and temporal sound structure depended on species of plants. In addition, individual difference of mastication intervals observed in the two manatees was probably due to different body sizes. Overnight recording showed that both manatees kept feeding for more than 0.5 hours followed by 1.6 ± 1.3 hours interruption of feeding. Other sounds such as insect calls, rainfall, and vocalizations of other manatees could be useful to understand habitat selection, weather and presence of conspecifics. Acknowledgment Research and Development Program for New Bio-industry Initiatives

SEROEPIDEMIOLOGY OF TmPV1 INFECTION IN CAPTIVE AND WILD FLORIDA MANATEES (TRICHECHUS MANATUS LATIROSTRIS)

In 1997, cutaneous papillomatosis caused by Florida manatee (Trichechus manatus latirostris [Tm]) papillomavirus 1 (TmPV1) was detected in seven captive manatees at the Homosassa Springs Wildlife State Park, Florida, USA, and, subsequently, in two wild manatees from the adjacent Homosassa River. Since then, papillomatosis has been reported in captive manatees housed in other locations, but not in wild animals. To determine TmPV1 antibody prevalence in captive and wild manatees sampled at various locations throughout Florida coastal regions, virus-like particles, composed of the L1 capsid protein of TmPV1, were generated with a baculovirus expression system and used to measure anti-TmPV1 antibodies in an enzyme-linked immunosorbent assay. Serologic analysis of 156 manatees revealed a TmPV1 antibody prevalence of 26.3%, with no significant difference between captive (n=39) and wild (n=117) manatees (28.2% and 25.6%, respectively). No antibody-positive wild animal showed PV-induced cutaneous lesions, whereas papillomatosis was observed in 72.7% of antibody-positive captive manatees. Our data indicate that Florida manatees living in the wild are naturally infected by TmPV1 but rarely show TmPV1-induced papillomatosis. Hence, it appears that the wild population would not be harmed in a case of contact with captive animals without visible lesions and productive infections, which could be thus released into the wild.

Secretion of anti-Müllerian hormone in the Florida manatee Trichechus manatus latirostris, with implications for assessing conservation status

Environmental and anthropogenic stressors can affect wildlife populations in a number of ways. For marine mammals (e.g. the Florida manatee Trichechus manatus latirostris), certain stres- sors or conservation risk factors have been identified, but sublethal effects have been very difficult to assess using traditional methods. The development of 'biomarkers' allows us to correlate effects, such as impaired reproduction, with possible causes. A recently developed biomarker (anti-Mullerian hor- mone, AMH) provides an enzyme-linked immunosorbent assay of gonadal function. The study objec- tive was to determine AMH levels in wild manatees. In total, 28 male and 17 female manatee serum samples were assayed. Animal demographics included collection date, body weight (kg) and total length (cm). In certain cases, age of individuals was also known. AMH levels ranged from 160 to 2451.85 ng ml -1 (mean = 844.65 ng ml -1 ) in males and 0.00 to 0.38 ng ml -1 (mean = 0.10 ng ml -1 ) in females. Linear regression analyses revealed a significant relationship between male AMH levels and body weight (R 2 = 0.452; p < 0.001) and length (R 2 = 0.338; p < 0.001). Due to the small sample size, regression analyses for female AMH and body weight and length were not significant. This rep- resents the first report of AMH detection in a marine mammal. AMH levels in male manatees are the highest of any species observed to date, whereas levels in females are within reported ranges. Fur- ther studies will promote improved conservation decision by assessing AMH levels in the manatee as a function of various stressors including, but not limited to, nutritional status, serious injuries (e.g. watercraft collisions), exposure to biotoxins or contaminants, or disease.

Meeting the Manatee Challenge: The Feasibility of Using Crittercam on Wild Manatees

The West Indian manatee, Trichechus manatus, is currently listed as an endangered species throughout its range. Threats to the subspecies in Florida include watercraft collisions, the potential loss of warm water refuges, exposure to harmful algal blooms, entanglement in fishery gear, habitat degradation, freshwater diversions and withdrawals, and the crushing or isolation caused by water control structures. A study was initiated in 2001 to investigate several of these threats and develop methods to aid in endangered species recovery needs by exploring the feasibility of using Crittercam, an animal-borne imaging and data-collection device, on Florida manatees. While the actual Crittercam technology was appropriate for the goals of this study, the unique morphology of the species and its variable habitat made finding a method of attachment extremely challenging. An appropriate and reliable method of attachment to the manatee is necessary for the successful application of animal-borne imaging data collection. Methods previously used successfully on other species were explored, including various combinations of suction cups and adhesives, a nylon harness and a peduncle belt with a trailing tether. Over a span of several years, captive trials and field testing determined that the peduncle belt with connecting tether was the most appropriate method of attachment. Several iterations of this design were made in order to provide the necessary functionality for ensuring productive research with the Crittercam on wild manatees.

An isotopic assessment of the feeding habits of free-ranging manatees

There is relatively little information available on how the relative importance of fresh, brackish, or marine environments may vary geographically or individually with respect to manatee Trichechus manatus latirostris feeding ecology. As a first application of stable isotope analysis to determine diet composition of wild manatees, skin from 25 manatee carcasses and leaf tissue from 25 plant species were collected from 4 regions in Florida and analyzed for relative values of stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopes. Values of δ 13 C and δ 15 N measured in plants ranged from -0.8 ± 1.0 to 6.4 ± 0.0‰ and in manatee tissues from -8.7 ± 0.2 to -28.3 ± 0.1‰, respectively. A mix- ing model was applied to estimate manatee diet composition across different geographic regions, and results (mean, all manatees, all regions) indicated that, overall, Florida manatees consumed 44% of their diet from marine and/or estuarine sources. Manatees living along the central east coast obtained 100% of their diet from marine and/or estuarine sources, while animals recovered from the St. John's River system (NE region) obtained ~50% of their diet from freshwater sources, suggesting that some time had been spent outside of the river basin. In conclusion, results of the stable isotope analysis suggest that, even though manatees have a physiological requirement to ingest fresh water, marine and estuarine environments supply a significant fraction of their food resources.

ELECTROCARDIOGRAPHY IN TWO SUBSPECIES OF MANATEE (TRICHECHUS MANATUS LATIROSTRIS AND T. M. MANATUS)

Electrocardiographic (ECG) measurements were recorded in two subspecies of awake, apparently healthy, wild manatees (Trichechus manatus latirostris and T. m. manatus) undergoing routine field examinations in Florida and Belize. Six unsedated juveniles (dependent and independent calves) and 6 adults were restrained in ventral recumbency for ECG measurements. Six lead ECGs were recorded for all manatees and the following parameters were determined: heart rate and rhythm; P, QRS, and T wave morphology, amplitude, and duration; and mean electrical axis (MEA). Statistical differences using a t-test for equality of means were determined. No statistical difference was seen based on sex or subspecies of manatees in the above measured criteria. Statistical differences existed in heart rate (P = 0.047), P wave duration (P = 0.019), PR interval (P = 0.025), and MEA (P = 0.021) between adult manatees and calves. Our findings revealed normal sinus rhythms, no detectable arrhythmias, prolonged PR and QT intervals, prolonged P wave duration, and small R wave amplitude as compared with cetacea and other marine mammals. This paper documents the techniques for and baseline recordings of ECGs in juvenile and adult free-living manatees. It also demonstrates that continual assessment of cardiac electrical activity in the awake manatee can be completed and can be used to aid veterinarians and biologists in routine health assessment, during procedures, and in detecting the presence of cardiac disease or dysfunction.

Differential response by manatees to playbacks of sounds simulating approaching vessels

One of the most pressing concerns associated with the endangered Florida manatee is mortality due to collisions with watercraft. Watercraft collisions are the leading identified cause of adult mortality, resulting in greater than 30% of manatee deaths each year. Reducing adult mortalities is critical to the recovery of the manatee population, as population trends are more sensitive to adult deaths than to those of other age groups. Acoustic playback experiments were conducted to assess the behavioral responses of manatees to watercraft approaches. Playback stimuli were constructed to simulate a vessel approach to approximately 10 m in seagrass habitats. Stimulus categories were (1) silent control; (2) idle outboard approach; (3) planing outboard approach; and (4) fast personal watercraft approach. These results are the first to document responses of wild manatees to playback stimuli. Analyses of swim speed, changes in behavioral state, and respiration rate indicate that the animals respond differentially to the playback categories. The most pronounced responses, relative to the controls, were elicited by the personal watercraft. Quantitative documentation of response during playbacks will provide data that may be used as the basis for future models to predict the impact of specific human activities on manatee and other marine mammal populations.

PREHENSILE USE OF PERIORAL BRISTLES DURING FEEDING AND ASSOCIATED BEHAVIORS OF THE FLORIDA MANATEE (TRICHECHUS MANATUS LATIROSTRIS)

AbstractThe use of perioral bristles (modified vibrissae) by 17 captive Florida manatees and approximately 20 wild manatees was analyzed. Captive manatees were fed six species of aquatic vegetation normally eaten in the wild (four freshwater species and two seagrasses). Inanimate objects were placed in the holding tanks with manatees at Lowry Park Zoological Gardens (Tampa, FL) to determine the degree to which perioral bristles were used in exploration and to define the range of manipulative behavior. In addition, behavioral observations were made on the use of perioral bristles during social interactions with conspecifics. Observations were recorded using a Hi8‐format video camera. Florida manatees possess an unusually large degree of fine motor control of the snout and perioral bristles. The large and robust perioral bristle fields of the upper lip were used in a prehensile manner during feeding. Bristle use by manatees feeding on submerged vegetation differed from that seen during feeding on floating vegetation. Other behavioral use of the perioral bristles shows variation depending upon the situation encountered. The degree of plasticity of perioral bristle use supports our hypothesis that the vibrissal‐muscular complex of the Florida manatee has evolved to increase the efficiency of grazing and browsing on aquatic vegetation and to fully maximize the potential of the manatee as a generalist feeder. The manipulative and sensitive nature of the manatee snout is likely a manifestation of a complex sensory and motor system which has evolved for marine mammal aquatic herbivores living in shallow turbid habitats.