Manatee Research Articles

Morphometric and structural analysis of Florida manatee spermatozoa.

Sperm characteristics, such as sperm morphology and sperm morphometry are important in assessing sperm quality. This is especially important for the management and conservation of endangered and exotic species, like the Florida manatee, where information of this nature is extremely limited. In this study, we fill this knowledge gap to better understand the reproductive physiology of Florida manatees by conducting the first extensive analysis of sperm morphometry and ultrastructure. Sperm were retrieved from the vas deferens of nine recently deceased Florida manatees. Computer‐aided sperm morphology analysis (CASMA) was used for morphometric analysis and laser‐scanning confocal microscopy and electron microscopy were used for structural and ultrastructural characterization. Our findings reveal new morphometric and structural data for the Florida manatee spermatozoon. Twelve morphometric features of Florida manatee sperm were quantified with some approximately 1.5–2 times larger than those previously reported. Ultrastructurally, the Florida manatee spermatozoon followed a mammalian structural pattern with an ovate‐shaped head, midpiece containing 84–90 mitochondria, and a flagellum. However, unique ultrastructural features were identified. Distinct, rectangular‐like enlargement of four outer dense fibers surrounding the axoneme was evident, which may provide additional tensile strength to counteract the forces on sperm transiting the female reproductive tract. Likewise, strong localization of F‐actin fibers within the midpiece may function to maintain sperm integrity within the female reproductive tract. These findings highlight the potential effects of sexual selective pressures on sperm size and structure in the Florida manatee and provide avenues for research on the occurrence of sperm competition in this species.

Lipidomics reveals specific lipid molecules associated with cold stress syndrome in the Florida manatee (Trichechus manatus latirostris)

Cold stress syndrome (CSS) in the Florida manatee (Trichechus manatus latirostris) results in perturbations to many physiological pathways, often leading to further illness or death. In this study, we applied a non-targeted lipidomics approach with ultra-high performance liquid chromatography and high-resolution tandem mass spectrometry to characterize changes related to CSS in the lipidomic profiles of manatee plasma. Lipidomic analyses were conducted on healthy manatee (control) and cold-exposed manatee plasma samples with varying concentrations of Serum Amyloid A (SAA), an acute-phase protein that is associated with inflammatory disease. Control manatees (n = 10) were compared to all manatees exposed to cold temperatures (n = 17), and a subset of those manatees with SAA values > 120 μg/mL (n = 9). Increased SAA values were associated with higher levels of various acylcarnitine lipids, while several triacylglycerols and oxidized triacylglycerols were significantly lower in manatees with cold exposure. These identified lipids are critical molecules involved in the maintenance of energy homeostasis and could potentially be examined in conjunction with current physical parameters to characterize cold stress. The ability to detect such differences highlights the addition of lipidomics as a valuable tool in understanding cold stress and potentially other illnesses in manatees. Further investigation into the function of the altered lipids could greatly increase our understanding of lipid metabolism in physiologically stressed manatees as well as other marine mammals and inform future management recovery strategies.

“See nothing but beauty”: The shared work of making anthropogenic destruction invisible to the human eye

The Florida Tampa Electric Company’s Manatee Viewing Center (MVC) and its fossil-fuelled Big Bend power plant are separated by a narrow ship channel that serves as state and federal sanctuary for threatened Florida Manatees. As humans have destroyed much of their warm spring habitat, many manatees are forced to rely on power plant hot water effluent to survive during cold winter months. Visitors’ reactions to the MVC are every bit as incongruous as a massive greenhouse gas pollutant source enabling a wildlife reserve. Notwithstanding its inescapable presence, visitor reviews of the MVC nearly uniformly ignore the immense power plant. We offer this study of online reviews of the MVC to examine how and why everyday people’s interactions are fundamental to making dominant practices of anthropogenic ecological destruction unremarkable and, therefore, unfixable. Specifically, we argue the collective blindness reflected in the findings of this study exemplifies a broader sociocultural tendency to articulate and reinforce spaces of ecological “invisibility.” In such spaces, our quotidian practices and discourses play a central role in enabling collective environmental inattention and environmental inaction, especially when we are confronted with places in which the constructed binary between human and “natural” realms spectacularly collapses.

Spatiotemporal dynamics of mangrove forest and association with strandings of Antillean manatee (Trichechus manatus) calves in Paraíba, Brazil

AbstractEstuaries in Brazil are highly threatened environments and habitat loss is the main influential factor for the increase in the number of strandings of Antillean manatee (Trichechus manatus) calves in the north-eastern region of the country. The aim of the present study was to analyse and quantify the spatiotemporal dynamics of mangroves in the state of Paraíba and the association with manatee calf stranding events. The study area encompassed 10 remaining mangroves along the coast of the state, four of which were located within protected areas. Information on the mangrove forests was obtained from satellite images from the last four decades. Data on stranded Antillean manatee calves were obtained from a databank with records from 1980 to 2019. The data were analysed using geoprocessing techniques and statistical analyses. The results demonstrated changes in the mangrove forest over time, with larger areas existing during the 1980s, reductions in the following periods but a slight increase in the last decade. The number of stranded Antillean manatee calves increased over the years, with stranding events concentrated mainly on the northern coast of the state. The smallest number of stranding events occurred in the 1980s, when the mangrove forests were larger. Our findings confirm that the integrity of mangroves is of extreme importance to the maintenance and sustainability of Antillean manatee populations.

Chronic exposure to glyphosate in Florida manatee

Florida manatees depend on freshwater environments as a source of drinking water and as warm-water refuges. These freshwater environments are in direct contact with human activities where glyphosate-based herbicides are being used. Glyphosate is the most used herbicide worldwide and it is intensively used in Florida as a sugarcane ripener and to control invasive aquatic plants. The objective of the present study was to determine the concentration of glyphosate and its breakdown product, aminomethylphosphonic acid (AMPA), in Florida manatee plasma and assess their exposure to manatees seeking a warm-water refuge in Crystal River (west central Florida), and in South Florida. We analyzed glyphosate’s and AMPA’s concentrations in Florida manatee plasma (n = 105) collected during 2009–2019 using HPLC-MS/MS. We sampled eight Florida water bodies between 2019 and 2020, three times a year: before, during and after the sugarcane harvest using grab samples and molecular imprinted passive Polar Organic Chemical Integrative Samplers (MIP-POCIS). Glyphosate was present in 55.8% of the sampled Florida manatees’ plasma. The concentration of glyphosate has significantly increased in Florida manatee samples from 2009 until 2019. Glyphosate and AMPA were ubiquitous in water bodies. The concentration of glyphosate and AMPA was higher in South Florida than in Crystal River, particularly before and during the sugarcane harvest when Florida manatees depend on warm water refuges. Based on our results, Florida manatees were chronically exposed to glyphosate and AMPA, during and beyond the glyphosate applications to sugarcane, possibly associated with multiple uses of glyphosate-based herbicides for other crops or to control aquatic weeds. This chronic exposure in Florida water bodies may have consequences for Florida manatees’ immune and renal systems which may further be compounded by other environmental exposures such as red tide or cold stress.

In‐Water Bridge Construction Effects on Manatees with Implications for Marine Megafauna Species

ABSTRACTGlobally, increasing coastal development requires construction and maintenance of transportation infrastructure that affects terrestrial and aquatic ecosystems. Construction of bridges as part of transportation networks introduces a series of risks to aquatic species near construction zones. We reviewed relevant literature and obtained exemplary case studies to synthesize potential effects of bridge construction on the West Indian manatee (Trichechus manatus), a nearshore megafauna species vulnerable to human activities. Stages of bridge construction including dredging, pile driving, and installation and assembly of bridge components each involve potential direct and indirect effects on manatees. Direct effects such as vessel interactions, entanglement or ingestion, and entrainment may result in acute physical injury or mortality. Indirect effects from construction such as habitat obstruction or degradation and increased noise from construction activities can alter behavior and intraspecies communication and reduce access to essential resources. Some effects of construction may be immediately difficult to quantify, but cumulative effects through time can result in major habitat and species loss. To prevent large‐scale negative effects of construction on manatees and other aquatic species, use and evaluation of mitigation strategies should be implemented pre‐, during, and post‐construction. As the global human population increasingly occupies coastal zones, effective planning of coastal development, including bridge and other in‐water construction, will be essential to support conservation and recovery efforts for manatees and other species at risk in these areas. © 2021 The Wildlife Society.

Investigating an increase in Florida manatee mortalities using a proteomic approach

Two large-scale Florida manatee (Trichechus manatus latirostris) mortality episodes were reported on separate coasts of Florida in 2013. The east coast mortality episode was associated with an unknown etiology in the Indian River Lagoon (IRL). The west coast mortality episode was attributed to a persistent Karenia brevis algal bloom or ‘red tide’ centered in Southwest Florida. Manatees from the IRL also had signs of cold stress. To investigate these two mortality episodes, two proteomic experiments were performed, using two-dimensional difference in gel electrophoresis (2D-DIGE) and isobaric tags for relative and absolute quantification (iTRAQ) LC–MS/MS. Manatees from the IRL displayed increased levels of several proteins in their serum samples compared to controls, including kininogen-1 isoform 1, alpha-1-microglobulin/bikunen precursor, histidine-rich glycoprotein, properdin, and complement C4-A isoform 1. In the red tide group, the following proteins were increased: ceruloplasmin, pyruvate kinase isozymes M1/M2 isoform 3, angiotensinogen, complement C4-A isoform 1, and complement C3. These proteins are associated with acute-phase response, amyloid formation and accumulation, copper and iron homeostasis, the complement cascade pathway, and other important cellular functions. The increased level of complement C4 protein observed in the red tide group was confirmed through the use of Western Blot.

Baseline urinalysis results in 32 healthy Antillean manatees (Trichechus manatus manatus).

To describe results of analysis of free-catch urine samples collected from Antillean manatees (Trichechus manatus manatus) under human care in the Caribbean. 32 Antillean manatees in 5 Caribbean oceanaria and rescue centers. Urine samples were obtained by opportunistic free catch during physical examination or through the use of operant conditioning procedures. Urinalyses consisted of macro- and microscopic evaluations, biochemical analyses with test strips, and refractometry. Results were compared for manatees grouped on the basis of age, sex, and habitat. Urine samples were typically clear, straw colored, and alkaline (mean pH, 8.0); had a urinoid odor and low specific gravity (mean, 1.010); and had results on qualitative test strips that were consistently negative for the presence of glucose, bilirubin, ketones, proteins, nitrites, RBCs, and WBCs. Microscopically, the mean ± SD number of RBCs and WBCs/hpf was 0.5 ± 0.3 RBCs/hpf and 1.1 ± 1.5 WBCs/hpf. The presence of some epithelial cells and crystals was typical. Spermatozoa were found in urine from 1 of 15 sexually mature males, and parasite larvae and eggs were found in urine from 2 manatees. Results of the present study yielded the first compilation of baseline urinalysis values in healthy Antillean manatees under human care, which, when combined with physical examination and other diagnostic procedures, can help in monitoring the health of these animals. We encourage the use of free-catch urine collection methods, as used in the present study, for routine urinalyses of manatees under human care in zoos, aquaria, or rescue centers.

The evolutionary history of manatees told by their mitogenomes

The manatee family encompasses three extant congeneric species: Trichechus senegalensis (African manatee), T. inunguis (Amazonian manatee), and T. manatus (West Indian manatee). The fossil record for manatees is scant, and few phylogenetic studies have focused on their evolutionary history. We use full mitogenomes of all extant manatee species to infer the divergence dates and biogeographical histories of these species and the effect of natural selection on their mitogenomes. The complete mitochondrial genomes of T. inunguis (16,851 bp), T. senegalensis (16,882 bp), and T. manatus (16,882 bp), comprise 13 protein-coding genes, 2 ribosomal RNA genes (rRNA - 12S and 16S), and 22 transfer RNA genes (tRNA), and (D-loop/CR). Our analyses show that the first split within Trichechus occurred during the Late Miocene (posterior mean 6.56 Ma and 95% HPD 3.81–10.66 Ma), followed by a diversification event in the Plio-Pleistocene (posterior mean 1.34 Ma, 95% HPD 0.1–4.23) in the clade composed by T. inunguis and T. manatus; T. senegalensis is the sister group of this clade with higher support values (pp > 0.90). The branch-site test identified positive selection on T. inunguis in the 181st position of the ND4 amino acid gene (LRT = 6.06, p = 0.0069, BEB posterior probability = 0.96). The ND4 gene encodes one subunit of the NADH dehydrogenase complex, part of the oxidative phosphorylation machinery. In conclusion, our results provide novel insight into the evolutionary history of the Trichechidae during the Late Miocene, which was influenced by geological events, such as Amazon Basin formation.

The role of touch in captive and semi-captive Antillean manatees (Trichechus manatus manatus)

Abstract Tactile signals have been neglected in aquatic animal studies despite being a major communication modality. We investigated Antillean manatees’ tactile behavioural repertoire and budget in captivity (7-females and 4-males) and semi-captivity (4-males) in Brazil. We detected 17 tactile behaviours (14.03% of the activity budget) with social, self-maintenance, or environmental exploration functions. The observation method influenced the detection of self-maintenance behaviours — focal animal and ad libitum detected more of these behaviours than scan sampling. Age, sex, housing, and centre routines influenced the tactile repertoire. The captive females and semi-captive males tactile patterns differed, suggesting that sex and animal-pool density play a role in tactile patterns. We recommend carefully choosing the observation method when investigating functional categories of manatee tactile behaviours. The monitoring and stimulation of manatee tactile behaviours should integrate rehabilitation and reintroduction practices. Environmental enrichment may stimulate tactile behaviours related to habitat exploration, key behaviours in aiding manatee navigation.

DNA Sequence Analyses Reveal Two New Species of Caloglossa (Delesseriaceae, Rhodophyta) from the Skin of West Indian Manatees

Epizoic macroalgae collected from the skin of West Indian manatees included specimens of the red algal family Delesseriaceae. Morphological and rbcL sequence analyses indicated that these specimens represented two novel species of Caloglossa. One species, described here as Caloglossa kamiyana Freshwater, Cath.E. Miller & Frankovich sp. nov., had been previously studied and recognized as part of the C. ogasawaraensis species complex. The rbcL sequence divergence between C. kamiyana and other taxa within the complex ranged from 4.6–5.3%, and tetrasporangial mother cells are cut off from the lateral pericentral cells by oblique divisions instead of transverse divisions as in C. ogasawaraensis. The second species was resolved as a closely related sister species to C. fluviatilis, with a minimum interspecific sequence divergence of 2.0%. It was morphologically indistinguishable from C. fluviatilis except for one potential character—mostly one, instead of multiple rhizoids, developing from rhizoid-bearing pericentral and marginal wing cells. It is herein described as Caloglossa manaticola Freshwater, Cath.E. Miller & Frankovich sp. nov.

Reconstructing population dynamics of a threatened marine mammal using multiple data sets

Models of marine mammal population dynamics have been used extensively to predict abundance. A less common application of these models is to reconstruct historical population dynamics, filling in gaps in observation data by integrating information from multiple sources. We developed an integrated population model for the Florida manatee (Trichechus manatus latirostris) to reconstruct its population dynamics in the southwest region of the state over the past 20 years. Our model improved precision of key parameter estimates and permitted inference on poorly known parameters. Population growth was slow (averaging 1.02; 95% credible interval 1.01–1.03) but not steady, and an unusual mortality event in 2013 led to an estimated net loss of 332 (217–466) manatees. Our analyses showed that precise estimates of abundance could be derived from estimates of vital rates and a few input estimates of abundance, which may mean costly surveys to estimate abundance don’t need to be conducted as frequently. Our study also shows that retrospective analyses can be useful to: (1) model the transient dynamics of age distribution; (2) assess and communicate the conservation status of wild populations; and (3) improve our understanding of environmental effects on population dynamics and thus enhance our ability to forecast.

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.

Nematode epibionts on skin of the Florida manatee, Trichechus manatus latirostris

A survey for the presence of nematodes on the skin of the native Florida manatee, Trichechus manatus latirostris from Crystal River, Florida was conducted during annual manatee health assessments. A putative isolate of Cutidiplogaster manati (Diplogastridae) and two other nematodes belonging to the same family were recovered from mid-dorsal tail skin-scrapings from all sampled winter-collected healthy wild adult manatees during two successive years (2018–2019). Qualitative abundance estimates of these three species of diplogastrid nematodes suggest that an average wild Florida manatee adult might possess between 30,000 and 120,000 nematodes on its tail dorsum and that the entire body dorsum including the tail might possess 160,000–640,000 nematodes in roughly equal ratios. Attempts to culture these nematodes on a variety of different culture media were unsuccessful but examination of the mouth (stomatal) morphology suggests specialized feeding on microbes such as diatoms or predation on other nematodes. No skin lesions were observed during the 2018–2019 samplings suggesting that under normal conditions these nematodes are highly specialized free-living epibionts of the skin that are tightly bound to this niche and horizontally transferred between individual manatees in an analogous fashion to human skin mites (Demodex folliculorum and D. brevis). Molecular phylogenetic inferences using sequences of near full length SSU and D2–D3 expansion segments of LSU rRNA genes revealed a putative new morphospecies in Cutidiplogaster sister to C. manati that was monophyletic with several named Mononchoides species, and another putative new morphospecies that formed a clade with several undescribed species similar in appearance to Mononchoides as well as Tylopharyx, Eudiplogasterium, Paroigolaimella and Sachsia.

Genetic Connectivity of the West Indian Manatee in the Southern Range and Limited Evidence of Hybridization With Amazonian Manatees

The Antillean subspecies of the West Indian manatee is classified as endangered by the International Union for the Conservation of Nature (IUCN) Red List. In Brazil, the manatee population is listed as endangered with an estimated population size of 500–1,000. Historic hunting, recent habitat degradation, and fisheries bycatch have decreased the population size. The Amazonian manatee is listed as vulnerable by the IUCN with unknown population sizes within Brazil. The Antillean manatee occurs in sympatry with the Amazonian manatee in Brazil and hybridization has been previously indicated. To provide information on the genetic structure, diversity, and degree of hybridization in the sympatric zone near the Amazon River mouth, the mitochondrial DNA control region and 13 nuclear microsatellite markers were assessed on the two species. Samples were analyzed from the Antillean subspecies across its distribution in Brazil (n= 78) and from the Amazonian species (n= 17) at the Amazon River mouth and inland mainstem river. To assess the previously defined evolutionary significant units of Antillean manatees in the area, an additional 11 samples from Venezuela and Guyana were included. The Antillean manatee was found to be a single population in Brazil and had lower than average number of alleles (3.00), expected heterozygosity (0.34), and haplotype diversity (0.15) when compared to many other manatee populations. The low values may be influenced by the small population size and extended pressures from anthropogenic threats. Gene flow was identified with Venezuela/Guyana in admixed Antillean Brazil samples, although the two populations were found to be moderately divergent. The nuclear loci in Venezuela/Guyana Antillean manatee samples indicated high differentiation from the samples collected in the Amazon River (FST= 0.35 andRST= 0.18,p= 0.0001). No indication of nuclear hybridization was found except for a single sample, “Poque” that had been identified previously. The distribution of Antillean manatees in Brazil is extensive and the areas with unique habitat and threats would benefit from independent management and conservation actions. Gene flow, resulting in genetic diversity and long-term population stability, could be improved in the southern range through habitat restoration, and the establishments of travel corridors and protected areas, which are particularly important for successful parturition and neonatal calf survival.

TLR4 and TLR8 variability in Amazonian and West Indian manatee species from Brazil.

Amazonian (Trichechus inunguis) and West Indian (Trichechus manatus) manatees are aquatic mammals vulnerable to extinction found in the Amazon basin and the coastal western Atlantic. Toll-like receptors (TLR) play a key role in recognizing pathogen-associated molecular patterns using leucine-rich repeats (LRRs). We described the diversity of TLR4 and TLR8 genes in these two species of manatee. Amazonian manatee showed seven SNPs in TLR4 and the eight in TLR8, while West Indian manatee shared four and six of those SNPs, respectively. In our analysis, TLR4 showed one non-conservative amino acid replacement substitution in LRR7 and LRR8, on the other hand, TLR8 was less variable and showed only conserved amino acid substitutions. Selection analysis showed that only one TLR4 site was subjected to positive selection and none in TLR8. TLR4 in manatees did not show any evidence of convergent evolution compared to species of the cetacean lineage. Differences in TLR4 and TLR8 polymorphism may be related to distinct selection by pathogens, population reduction of West Indian manatees, or an expected consequence of population expansion in Amazonian manatees. Future studies combining pathogen association and TLR polymorphism may clarify possible roles of these genes and be used for conservation purposes of manatee species.

Conservation issues using discordant taxonomic and evolutionary units: a case study of the American manatee (

The delimitation of evolutionarily significant units (ESUs) frequently results in controversy, but prioritising populations with evolutionary independence is essential for effective in situ conservation management. The American manatee (Trichechus manatus) is distributed along subtropical and tropical coastal waters from Florida (USA) to Alagoas (Brazil), and two subspecies are traditionally recognised, namely, T. m. latirostris, restricted to the Florida peninsula, and T. m. manatus, found in the remaining areas. However, this subspecific classification is not supported by genetic and morphologic evidence, which, rather, recognises two deeply differentiated populations or ESUs called Atlantic (Brazil) and Caribbean (from Venezuela to Florida). In this viewpoint paper, we compare both intraspecific divisions of T. manatus and the conservation implications. First, we used all available mtDNA evidence to test the genealogical clustering of the two American manatee ESUs by using a tree-based coalescent method. Second, we have used different models under a coalescent framework to estimate the historic gene flow among manatee populations. The analysis of the spatial distribution of mtDNA clusters confirmed the existence of the two suggested ESUs, rather than the two claimed subspecies. Furthermore, the best model to explain historic migration indicates that Brazilian manatees belong to an isolated population, whereas Florida and Caribbean populations are connected by more recent gene flow. These results have confirmed that T. manatus of the Caribbean, Gulf of Mexico and Florida belong to the same deme or Caribbean ESU, and the relatively isolated population inhabiting the Atlantic coast of Brazil belongs to the Atlantic ESU. Furthermore, both ESUs are separated by an interspecific hybrid zone (with the Amazonian manatee) located around the mouth of the Amazon River towards the Guianas coastline. The subdivision of two ESUs is also highly supported by karyotypic, morphological and ecological data, and is in clear disagreement with the traditional subspecies designations and the IUCN priorities, which manages Brazilian manatees as part of the Antillean manatee subspecies (T. m. manatus). Rather, Brazilian manatees should be considered as a full priority for conservation and require further taxonomic research; because of their deep history of isolation, they present high genetic and morphologic differentiation from all other American manatees.

Differing impact effects of extreme red tide algal blooms on mortality of Florida manatees

A significant cause of mortality in the endangered Florida Manatee (Trichechus manatus latirostris) is toxicity from the proliferation of aquatic algae Karenia brevis, known as Red Tide. Whilst several factors drive these so-called ‘Red Tide blooms’, the reasons for subsequent mass mortalities in manatees are not fully understood. We conducted a longitudinal analysis of existing case-by-case records of Red Tide effects on manatee mortality in coastal waters, estuaries and inland waterways of Florida, USA. We identify types of mortality events, some of which show predictability in location, seasonality, duration and impact on manatee mortality. Suggestions for monitoring and mitigation to reduce Red Tide impacts on manatees, from understanding predictable and exceptional instances of Red Tide algal blooms are provided.

Behavioural and physiological responses of captive Antillean manatees to small aerial drones

Abstract Context Unmanned aerial vehicles or drones are powerful tools for wildlife research. Identifying the impacts of these systems on target species during operations is essential to reduce risks of disturbance to wildlife, to minimise bias in behavioural data, and to establish better practices for their use. Aims We evaluated the responses of captive Antillean manatees to the overhead flight of a small aerial drone. Methods We used aerial and ground videos to compare manatee activity budgets and respiration rates in three 15-min sampling periods: ‘before’, ‘during’ and ‘after’ flights with a DJI Phantom 3 Advanced. The drone was hovered stationary for 3 min at five altitudes (100 m, 40 m, 20 m, 10 m, 5 m) to determine whether manatees display behavioural responses compared with the control period, and whether they respond more at lower altitudes. Only one flight was performed per manatee group to avoid bias owing to habituation to the drone. Key results Manatees responded to drone flights by (1) increasing their activity levels during and after flights, therefore signalling after effects; (2) decreasing their respiration rate during flights; and (3) displaying behavioural reactions including grouping, tail-kicking, fleeing from their original position and moving under submerged structures. From the 11 individuals displaying behavioral reactions, 9 reacted in the first ~2 min of flight, preventing assessments of altitude effects and suggesting manatees responded to the drone sound at take-off. Conclusions Behavioural changes of responding manatees were similar to previous reports of disturbance responses to boats and drones in this species. Our use of a control period showed shifts in respiration rates and activity budgets that persisted after flights. Several manatees reacted to the drone from the time of take-off and first minutes of flight, indicating that the sound of the electric rotors could be a strong negative stimulus to manatee and highlighting the importance of establishing safe distances for take-off. Implications Future studies should consider that drones could elicit conspicuous and inconspicuous responses in manatees. Our results emphasise the need for control data on animal behaviour to better assess the impact of drones on wildlife and to design non-invasive protocols.

Manatee Trichechus manatus latirostris calf mortality in Florida: a retrospective review of pathology data from 2009-2017.

High maternal investment and extended inter-calving intervals in Florida manatees Trichechus manatus latirostris make calf survivorship critical to overall population growth. However, detailed patterns of causes of mortality in calves have not been reported and state agency statistics report portions of perinatal mortality based on body length rather than actual cause of death (COD). The objectives of this study were to categorize COD based on necropsy data and geographical location in Florida for 1209 manatee calf carcasses (<236 cm total length) examined between January 2009 and December 2017 and to describe factors contributing to calf mortality. Results indicated COD was attributed to natural causes (47%, n = 573), cold stress syndrome (38%, n = 457), watercraft injury (13%, n = 155), or other human-related causes (2%, n = 24). Natural causes were the leading COD for small calves <151 cm, with death due to stillbirth or dystocia most frequent (48%, n = 273/573). Enteric trematodiasis contributed to a large proportion of deaths from natural causes in large calves within the southwest region of Florida, with an increasing annual trend. Brevetoxicosis contributed substantially to natural causes within the southwest region exclusively and was commonly comorbid with enteric trematodiasis. Cold stress syndrome was the leading cause of death for large calves (151-235 cm), with the Atlantic region having the highest proportion of cases. Watercraft injury was a sustained threat to large calves, especially within the southwest region. This report provides details on specific health threats and patterns of mortality among manatee calves.