Manatee Research Articles

Neonatal Abandonment and Hydrocephalus in Antillean Manatees (Trichechus manatus manatus): Is There a Causal Relationship?

Manatees are semi-social animals, with the mother-calf relationship being considered long-lasting for the species. However, some events lead to the separation of this pair. Orphaned manatee calves can be adopted by other females of the same species. However, if this does not happen and a healthy calf strand is rescued, immediate release represents the best option for the individual. But when immediate release becomes unviable, the animals are taken to rehabilitation centers and can die from various causes. A newborn Antillean manatee was rescued in the north of Brazil, and the attempt at immediate release was unsuccessful; three months later, the animal died. At necropsy, it was observed that the brain was soft and friable, collapsing when placed on a surface, with the corpus callosum region able to be ruptured easily and the cerebral hemispheres lying flaccid. The analysis of serial sections of the brain showed dilated lateral ventricles and a reduction in white matter, making it possible to affirm the presence of congenital hydrocephalus, the main factor that may have led to the abandonment of the offspring.

Enforcement of Clean Water Act Could Clean up Water, Save Florida Manatees

Enforcement of Clean Water Act Could Clean up Water, Save Florida Manatees

Evaluation of strategies for evidence-driven genome annotation using long-read RNA-seq.

While the production of a draft genome has become more accessible due to long-read sequencing, the annotation of these new genomes has not been developed at the same pace. Long-read RNA sequencing (lrRNA-seq) offers a promising solution for enhancing gene annotation. In this study, we explore how sequencing platforms, Oxford Nanopore R9.4.1 chemistry or PacBio Sequel II CCS, and data processing methods influence evidence-driven genome annotation using long reads. Incorporating PacBio transcripts into our annotation pipeline significantly outperformed traditional methods, such as ab initio predictions and short-read-based annotations. We applied this strategy to a nonmodel species, the Florida manatee, and compared our results to existing short-read-based annotation. At the loci level, both annotations were highly concordant, with 90% agreement. However, at the transcript level, the agreement was only 35%. We identified 4,906 novel loci, represented by 5,707 isoforms, with 64% of these isoforms matching known sequences in other mammalian species. Overall, our findings underscore the importance of using high-quality curated transcript models in combination with ab initio methods for effective genome annotation.

PROFOUND HYPOGLYCEMIA AND BLOOD GLUCOSE TESTING METHODOLOGIES IN FLORIDA MANATEES (TRICHECHUS MANATUS LATIROSTRIS) PRESENTED TO A CRITICAL CARE CENTER.

Florida manatees (Trichechus manatus latirostris) continue to experience pressure from various stressors that frequently result in the need for rescue and veterinary assistance. Interestingly, a subset of rescued manatees in critical condition exhibits profound hypoglycemia. The goals of this study were to enhance our understanding of this important aspect of manatee care by 1) characterizing the clinical presentation and factors associated with manatees that present with profound hypoglycemia, and 2) assessing agreement across blood glucose testing modalities [glucometer (whole blood), in-house bench-top analyzer (whole blood), a point of care analyzer (whole blood), and a local human hospital laboratory analyzer (serum)]. Twenty-five manatees were admitted to the Jacksonville Zoo and Gardens from 2017 to 2021. Seven manatees were profoundly hypoglycemic on presentation with blood glucose concentrations of < 30 mg/dL. Hypoglycemic manatees were admitted due to cold stress syndrome (n = 3; 1 calf, 2 adults) or emaciation consistent with an unusual mortality event (n = 4; 2 calves, 2 adults). Physical examination findings in hypoglycemic animals included emaciation (n = 7, 100%), lethargy (n = 7, 100%), and intermittent mild muscle fasciculations of the muzzle (n = 3, 42.8%). Hypoglycemia resolved with intense supportive care and monitoring in all affected animals within 32 h of admission. No associations were identified between hypoglycemia on presentation and life-stage, sex, transport distance to JZG's critical care facility, or rehabilitation outcome (death/euthanasia vs. release). Statistical agreement was observed between all blood glucose testing modalities except for the glucometer vs. the human hospital analyzer. Despite the limited sample size, these findings inform on the clinical presentation of severe hypoglycemia, the importance of close blood glucose monitoring after admission, blood glucose testing modalities, and clinical decision-making in Florida manatees admitted to critical care centers.

Historical ecology reveals the "surprising" direction and extent of shifting baselines for the Florida manatee (Trichechus manatus latirostis).

Historical data are often overlooked in risk assessments and recovery plans for marine animals, resulting in the "shifting baselines." Historical ecological studies demonstrate the "surprising" extent to which contemporary assumptions misrepresent premodern baselines. The Florida manatee, a subspecies of the West Indian manatee found primarily in Florida, USA, faces several existential threats, but risk assessments and recovery targets for the species are hindered by poor understanding of historical baselines. We conducted systematic and opportunistic reviews of archaeological and historical records of manatee occurrence in Florida, USA. Our data reveal that manatee populations in Florida were very small in the Precolonial and Colonial Periods, possibly representing infrequent in-migration from the Caribbean during favorable climate conditions. Manatees expanded in number and range across the Florida peninsula during the Territorial/Early Statehood and Early Modern Periods, first northward on the Atlantic Coast and later along the coast of the Gulf of Mexico. These expansions track increasing human populations, associated anthropogenic landscape alterations, and social and policy changes. Historical ecology is critical for "shaping a better Anthropocene" for humans and manatees in Florida.

Occurrence of Chiorchis fabaceus (Trematoda: Cladorchiidae) in a wild Antillean manatee (Trichechus manatus manatus): New parasitological data for this imperilled sirenian

Parasites impact wildlife populations and ecosystem health, thereby demanding regular monitoring. As part of the national conservation effort to preserve the free-ranging sirenians in Colombia, a parasitological survey was conducted between 2011 and 2023 on naturally deceased Antillean manatees (Trichechus manatus manatus). A total of 17 stranded carcasses were analysed for the occurrence of parasites. Herein, trematode adult stages were recovered from the stomach, small intestine, caecum and colon of an adult male manatee and microscopically analysed. Additionally, molecular analysis was conducted based on an almost complete coding sequence of the ITS1–5.8S-ITS2, partial sequence of 18S and 28S ribosomal DNA (rDNA) genes. Phylogenetic analysis clustered the trematode sequences within Chiorchis fabaceus species, thus constituting the first adult-based sequences isolated for the species. Presented data contribute to a better understanding of the sirenian parasite diversity.

Automatically Counting Florida Manatees (Trichechus manatus latirostris) from Drone Images Using Object-Based Image Analysis

Florida manatees (Trichechus manatus latirostris) require frequent and extensive surveys to inform conservation efforts. Crewed aircraft surveys can be costly, dangerous, and logistically complex. Unoccupied aerial systems (UASs) can assist with these issues. While manual review of UAS imagery can be time- and labor-intensive, automated detection of manatees in aerial survey footage can help. We present an object-based image analysis workflow for the automated detection and count of Florida manatees in Google Earth Engine, a free platform for research that allows for scripts and imagery sharing. Training and testing datasets were built from randomly extracted image frames from two stationary, unoccupied aerial system videos over thermal refugia. The workflow captured most manatees (93.98 to 95.62% recall; 4.38 to 6.03% false negative rate), but also counted many objects as manatees incorrectly (4.24 to 14.77% precision; 998.40 to 3,885.54% false positive over the detectable rate). Sun glint, mud plumes, and water close to shore were common causes of false positives. While the automated count was too high, the workflow lays markers over each detection, allowing for quick manual review for more accurate (semi-automated) counts. This study is an early step in automated detection tools for Florida manatees in a cloud-based platform. Future efforts could explore other platforms or may improve this workflow by including new classes for confounding objects.

Nutritional composition of manatee’s diet in the Western Caribbean: from the river to the reef

The endangered Greater Caribbean manatee (Trichechus manatus manatus), one of the largest aquatic herbivores in the Caribbean, plays a crucial role in nutrient recycling within the ecosystem, and the study of its feeding ecology is important for its conservation. Despite several studies determining the items consumed by manatees, there remains limited understanding of their nutritional significance for the species in the Western Caribbean. This study, aimed to analyze the bromatological composition of the food components in the manatee’s diet in the Mexican Caribbean across three distinct environments. We manually collected aquatic and semi-aquatic primary producers potentially part of the manatee diet in marine, brackish and riverine areas of the southern region of Quintana Roo, Mexico. Then, we analyzed them for moisture, crude protein, crude fiber, ash, ether extract, digestible nutrients, and digestible energy. We present the initial data on nutrient values in the manatee diet in the Caribbean, establishing a foundation for exploring the factors that influence spatial, temporal, and species-specific variations in nutrient content at a regional level. Our bromatological analysis demonstrated that the most nutritionally important plants for manatees, based mainly on protein content and freshwater contribution, include the seagrasses Halodule wrightii, Syringodium filiforme, Thalassia testudinum, the water lily Pontederia crassipes, and Vallisneria sp. Effective habitat management for manatees is crucial for their survival, ensuring that feeding resources are maintained in both enough quantity and high quality. Given its nutritional significance for manatees, we recommend that seagrasses in the region should be prioritized as conservation targets.

In vitro impacts of glyphosate on manatee lymphocytes

Exposure to contaminants, such as the herbicide glyphosate, can suppress protective immune functions. Glyphosate is the herbicide most used worldwide and has been found in the plasma of more than 50 % of the Florida manatees (Trichechus manatus latirostris) and all-year-round in their aquatic environment. Our objectives were to analyze the consequences of glyphosate exposure on their immune responses via T-lymphocyte proliferation assays and transcriptomics. We isolated peripheral blood mononuclear cells (mainly lymphocytes) of free-ranging manatees and performed T-cell proliferation assays. We used transcriptomics to understand the consequences of glyphosate in vitro exposure. The three doses chosen ranged from environmentally relevant concentrations at 10 to 10,000 µg.L−1 that is considered an environmental contamination scenario. Glyphosate caused a dose-dependent reduction in T-lymphocyte proliferation, with a significant mean reduction of 27.3 % at 10,000 µg.L−1 and up to 51.5 % in some individuals. Additionally, T-lymphocyte proliferation was significantly reduced in mid-winter compared to early winter. Transcriptomic analysis of peripheral blood mononuclear cells indicated that all doses of glyphosate (10, 1,000, and 10,000 µg.L−1) resulted in up-regulation of genes related to acute phase inflammation and inhibition of the T-lymphocyte proliferation pathway. Exposure to this contaminant along with other environmental stressors, such as extreme winters and red tide, might further affect the adaptive immune response of this threatened species.

Plastic pollution on beaches in an Antillean manatee conservation area, Brazil

The presence of plastic debris along shorelines is a widespread problem, and plastic debris can interact directly with marine wildlife. In northeast Brazil, the Antillean manatees are the most common marine mammals and use estuarine waters mainly as their home range. We aimed to investigate the characteristics of plastic debris on the estuarine-oceanic continuum and the accumulation density of plastic on beaches. The density of plastic debris on beaches located in transitional areas was 7–10-fold greater than that on beaches in estuarine and oceanic areas. Fragments were considered the most abundant form of plastic debris on all the beaches. Our findings could lead to improved pollution management in this marine protected area, principally due to the risks of remobilizing small plastic particles through tides and wind effects that scatter them in resting and feeding manatees areas.

Not Everyone Likes Manatees: Fishers' Perceptions Unveil Opportunities and Challenges for Manatee Conservation in the Swamp Complex of Ayapel, Colombia

ABSTRACTGreater Caribbean manatees Trichechus manatus manatus face complex conservation challenges throughout their distribution range, many of which are associated with human factors; and in consequence, the subspecies is considered Endangered (EN) by the International Union for Conservation of Nature (IUCN). Human‐related threats as hunting for meat consumption, collisions with boats, entanglement in fishing nets, pollution and loss of habitat put the Greater Caribbean manatee at risk in Colombia. Studies aiming to describe traditional knowledge and local perceptions provide information that can be useful to design local manatee conservation programmes. We analyse the fishers' perceptions regarding manatees in Ayapel, Córdoba. One hundred semi‐structured interviews were conducted, focusing on personal data, fishing practices, perceptions and knowledge about the manatees. According to the interviews, bycatch is the greatest threat to manatees (56%), followed by pollution (16%), whereas boat collisions (12%), hunting (11%) and drought (5%) are lower ranking threats. Our results demonstrated that participants have a good understanding of manatee biology and ecology. However, a human–manatee conflict was evidenced, as 39% of fishers consider that manatees negatively impact fishing by competition for the fishing resources and/or by damaging fishing gear. We recommend strengthening awareness about the importance of manatee to guarantee an optimal management of this subspecies and its habitat. Fishers should be directly involved in the formulation of management and conservation plans for the subspecies, as their knowledge becomes critical to understanding and mitigating the risks to manatee populations. This work has a clear application to understand the human factor in manatee recovery not only in our study area but also in other locations where manatees share habitat with people, particularly in marginalized human communities.

Seagrass mapping of north-eastern Brazil using Google Earth Engine and Sentinel-2 imagery

Seagrass ecosystems are globally important blue carbon sinks and support significant marine and terrestrial biodiversity. However, human-induced climate change coupled with other anthropogenic pressures have substantially reduced seagrass distributions, making them one of the most threatened ecosystems on Earth. The challenges associated with seagrass conservation include substantial data gaps and limited low-cost, near-real monitoring methods. To address these challenges, we used 507 Sentinel-2 satellite images, filtered between August 2020 and May 2021, in the Google Earth Engine cloud computing environment for regional scale seascape habitat mapping in north-eastern Brazil, a region where conservation efforts are particularly hampered by data limitations. We mapped 9452 km2 of coastline up to a depth of 10 m. We identified 328 km2 of seagrass ecosystems, providing vital open access positional information for a variety of research applications. We also assessed the capability of Sentinel-2 in monitoring temporal changes in coastal habitats, and revealed up to 15.9% declines in seagrass meadow coverage in specific areas over a five-year period in north-eastern Brazil. Our results demonstrate that Sentinel-2 is an effective tool in mapping seagrass distributions at a regional scale. The resulting maps are critical for supporting the conservation of Neotropical coastal biota, including the endangered Antillean Manatee. Our study emphasises the importance of replicable and systematic monitoring methods in the race to conserve threatened coastal ecosystems globally.

Age and sex effects on histological features and invitro culturing of Antillean manatee (Trichechus manatus manatus, Linnaeus 1758) dermis.

The biobanks from dermal biopsies represent an interesting strategy for biodiversity conservation. Nevertheless, the morphological and cellular patterns of the dermis can be influenced by the age and sex of the individual. Therefore, evaluating these factors is interesting for forming biobanks of Antillean manatees. These animals, representatives of marine fauna, have had their population reduced, and biobanks are essential for their conservation. Then, we evaluated the effects of age (3.5 years vs. 3.6-16 years vs. 23.6 years) and sex (males vs. females) on morphological and cellular parameters using histological and invitro culture techniques. Regardless of age, no differences were observed for dermal thickness, collagen fibres, tissue proliferative activity and viable cell recovery. Nonetheless, fibroblast reduction was observed in groups aged 23.6 years compared to other animals (p < 0.05). Additionally, cells from animals aged 3.6-16 years showed more significant mitochondrial damage than the other groups (p < 0.05). Regardless of sex, no differences were observed for dermal thickness, collagen fibres, tissue proliferative activity and viable cell recovery; however, females had fewer fibroblasts than males (p < 0.05). Cells from females showed lower mitochondrial damage when compared to cells from males. In summary, although age and sex do not influence dermal thickness and cell recovery, variations in the number of fibroblasts and mitochondrial characteristics were observed among the groups. These differences may be significant for understanding the dermis aspects to be correlated to biobank systems.

Long‐term tracking reveals the influence of body size and habitat type on the home range of Antillean manatees (Trichechus manatus manatus)

AbstractAntillean manatees (Trichechus manatus manatus) are endangered coastal, marine, and riverine megaherbivores with high environmental plasticity, constrained by tidal and seasonal water level cycles that affect access to food and fresh water. Accurate quantification of the species' habitat requirements, typically achieved through home range (HR) estimation, is required to implement area‐based conservation initiatives. In this study, we used GPS tracking data from 38 wild and captive‐rehabilitated released manatees to estimate HR using autocorrelated kernel density estimators (AKDE) and average time speed. We investigated whether body size, habitat type, sex and behavioural group influence home range size due to energy requirements, resources availability, a scramble‐competitive polygyny mating system, and adaptation to the wild. Eighteen manatees exhibited range‐resident behaviour, with a mean 95% home range of 72.96 km2 (± 218.52) and a median of 10.69 km2. The mean daily speed was estimated to be 13.47 km/day (± 4.16). Home range and body size were positively correlated, consistent with HR allometry theory. Long‐term tracked individuals showed a trend of increasing HR over time. Only four released animals (17.4%) were range‐resident, suggesting that they may need additional time to establish a home range. Individuals using only the marine environment had larger home ranges compared to mixed (marine and estuarine) and estuarine environments, probably due to freshwater availability. Our study contributes to the understanding of the factors driving manatee movement and provides more accurate estimates of area requirements, which can inform the establishment and zoning of marine protected areas.

Antillean manatees (Trichechus manatus) tolerate acute food deprivation associated with a modest reduction in body mass

Acute food deprivation induces metabolic shifts toward a greater reliance on lipid metabolism to sustain homeostasis in marine mammals. Lipid utilization depends on diet, metabolic rate, environmental conditions, and food availability. Antillean manatees ( Trichechus manatus) are aquatic herbivores with two-layered fat deposits that can reduce their metabolic rate by 23% when fasting. However, the contributions of lipid metabolism during fasting and refeeding in manatees remain poorly understood. Three juvenile Antillean manatees under human care were food deprived for 64 hours under close medical watch, then refed. Body mass (BM) was measured before and after acute food deprivation over the course of the four days of the study. Plasma samples were collected 16 hours post-prandial control, 40 and 64 hours after food deprivation, and 16 hours post-re-feeding. Prior to deprivation, mean BM was 107.3 ± 5.2 kg, and 100.1 ± 4.3 kg after deprivation. LDL increased after 40 hours of fasting and decreased at 64 hours, whereas HDL peaked at 60 hours post-fast and decreased during refeeding. TG and VLDL increased after refeeding; however, there were no significant changes between deprivation and refeeding in the lipid panel suggesting that 64 hours of acute food deprivation is well tolerated. These data provide an insight to the metabolic tolerance of the Antillean manatee that may experience acute periods of food deprivation as animals migrate across habitats and/or as they experience habitat loss or seasonal food scarcity. I. Ruiz was supported by NIH NIGMS URISE grant T34 GM145511. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Density and abundance estimation of West Indian manatee, Trichechus manatus, between the states of Ceará and Piauí, Northeast Brazil, using active acoustics

The West Indian manatee is one of the most threatened species in Brazil. The species has currently a patchy distribution from the state of Alagoas to the state of Amapá. The difficulty of observing manatees, especially in estuarine waters, is a challenge for conservation. Therefore, it is necessary to use new methodologies and technologies to solve manatee detection problems in their natural habitats. The goal of this study was to use an active acoustic method of detection to estimate manatee density and abundance in the estuarine complex of the Timonha and Ubatuba rivers, between the states of Ceará and Piauí, northeast Brazil. Data collection was conducted from a wooden boat with an outboard motor using a side-scan sonar. Sonar images were collected along line transects in three regions within the study area. Manatee abundance was calculated using distance sampling (Distance 6.0 software). There were 1,396 transection lines that totaled 863.6 km traveled in the study area. The observed general encounter rate was 0.089 group detected per kilometer traveled. The best detection model was the hazard-rate with no adjustment terms, resulting in a detection probability of 33.7%, and an estimated density for the entire study area of 9.19 manatees per km2. Abundance of manatees in the estuary was estimated to be 37 animals (CV% = 30.2, 95% CI = 21 - 66). The methodology using side-scan sonar proposed here was successful in the detection of manatees in the study area and in defining parameters for its use to estimate the population size using the distance sampling method. This study provides an estimate of manatee density and abundance in a key estuarine system along the northeast coast of Brazil, which can serve as a baseline for future studies and aid in the development of conservation strategies for the species. This is the first time this methodological approach has been used for manatee detection and abundance estimation in Brazil. We recommend the use of side-scan sonar in future West Indian manatee research.

Antillean manatee (Trichechus manatus manatus) occurrence and grazing spots in three protected areas of Costa Rica

The Antillean manatee is a poorly studied marine mammal in Costa Rica. Its distribution covers the entire Caribbean coast, but sighting reports are scarce. This research was conducted in three protected areas (PA) where the species is primarily observed. The objectives were to determine the density patterns of sightings and grazing spots; to explore the relationship between grazing spots and sightings with geographic and temporal variables, for PA separately; to study the frequency of sightings and grazing spots according to season, month, and period of the day, for PA together; and to determine the pertinence of using a marine ecology application MarEco to register manatee sightings by the public. Data on manatee sightings and grazing spots gathered with the MarEco app, under a citizen science mechanism, were complemented with data obtained by the Tortuguero Conservation Area Administration (TCAA) through other means. The number of sighting records registered through MarEco during nine months was alike to the number of records reported to the TCAA over six years in two of the PA studied. The areas with the highest density of grazing spots and sightings matched with studies conducted 10 to 20 years ago. In two of the PA, sightings were most often associated with the rainy season, while fresh grazing spots were specially counted from 6:00 h to 8:59 h. The results suggest that manatees exhibit high site fidelity in the three PA, that their increased presence during the rainy season is likely due to increased availability of food, and that they perform feeding activity predominantly at night.

Stranding reports of the Antillean manatee in the middle Magdalena Basin, Colombia 2011 to 2023

The aim of this study was to conduct an analysis of reported events concerning Antillean manatee (Trichechus manatus manatus) strandings in the middle Magdalena Basin region of Colombia from January 2011 to December 2023. To achieve this, a literature search was conducted in newspapers, news broadcasts, as well as gray and published reports, complemented by interviews and workshops with various governmental and non-governmental organizations. This search resulted in reliable information regarding past experiences involving stranded manatees over the years. Cases attended to by the environmental authority and its partners were also considered. Forty-four stranding events were recorded, with 34 deaths and 10 live manatees. Of the cases discovered, 79.5% of the reported cases were addressed. This effort highlighted the current lack of an official database that would provide firsthand knowledge of Antillean manatee stranding events in Colombia, thereby hindering timely and appropriate territorial management during response to the challenges faced by this species in the region. Furthermore, it underscores the need to implement a standardized response pathway for manatee cases, following appropriate protocols, and promoting the coordination of stakeholders within the regional stranding network in the middle Magdalena Basin. This approach, in addition to supporting the capacity building of communities, institutions, and organizations for improving response knowledge, conservation, and manatee recovery, is of paramount importance for the long-term sustainability of manatee populations in the region.

Perceptions on the distribution, threats, strandings, and conservation of the Antillean manatee (Trichechus manatus manatus) in the Río Dulce National Park, Izabal, Guatemala

The Antillean manatee in Guatemala faces multiple threats resulting from habitat loss and human interactions such as motorboat collisions and poaching. While some conservation efforts have been initiated in Río Dulce National Park (RDNP), there is a lack of studies examining the current perceptions of threats to the species. This knowledge gap may hinder the development of effective conservation strategies that consider both the species and local communities. Our objective was to analyze the perceptions of key local stakeholders concerning the Antillean manatee, including its distribution, threats, attention to strandings, and the current status of conservation in the protected area of RDNP. From July to October 2019, we conducted 50 semi-structured interviews with technicians and river users, such as fishermen and boat captains. Additionally, we held two workshops: one aimed at developing a participatory mapping exercise and another to validate the information. Each workshop was divided into two groups: one for technicians and another for river users. A total of 68 people participated in the workshops, the majority of respondents were male (n = 47), ranging in age from 19 to 71, and predominantly local to the area. Their activities in the river included fishing, biological monitoring, transportation, and providing tourism services. Perceived threats to the Antillean manatee included motorboat collisions, poaching, bycatch, habitat degradation, and water pollution. The focus groups also identified key observations, such as mother-calf sightings, specific areas of risk for manatee-boat collisions, areas with a higher presence of aquatic vegetation, and additional threats such as habitat degradation and poaching. Our results demonstrate that stakeholders possess a fundamental understanding of the manatee, its threats, and its distribution. They also highlight a noticeable lack of knowledge, specifically regarding the attention given to manatee strandings. It is recommended that conservation strategies include environmental education adapted to local conditions, as well as the promotion of manatee studies and their dissemination at the local level, including attention to strandings in the area.

Lipidomics and plasma hormone analysis differentiate reproductive and pregnancy statuses in Florida manatees (Trichechus manatus latirostris)

Florida manatees (Trichechus manatus latirostris) are protected as a threatened species, and data are lacking regarding their reproductive physiology. This study aimed to (1) quantify plasma steroid hormones in Florida manatees from two field sites, Crystal River and Indian River Lagoon, at different gestational stages and to (2) identify individual lipids associated with pregnancy status. Ultra-high performance liquid chromatography-tandem mass spectrometric analysis was used to measure plasma steroid hormones and lipids. Pregnant female manatees were morphometrically distinct from male and non-pregnant female manatees, characterized by larger body weight and maximal girth. Progesterone concentrations in manatees were also elevated during early gestation versus late gestation. Cholesterol, an important metabolic lipid, and precursor for reproductive steroids, was not different between groups. Mass spectrometry quantified 949 lipids. Plasma concentrations of glycerophospholipids, glycerolipids, sphingolipids, acylcarnitines, and cholesteryl esters were associated with pregnancy status in the Florida manatee. Most of the lipid species associated with pregnancy were triacylglycerides, phosphatidylethanolamines, and ether-linked phosphatidylethanolamines, which may serve as energy sources for fetal development. This research contributes to improving knowledge of manatee reproductive physiology by providing data on plasma steroid hormones relative to reproductive status and by identifying plasma lipids that may be important for pregnancy. Elucidation of lipid species directly associated with pregnancy has the potential to serve as a diagnostic approach to identify pregnant individuals in fresh and archived samples. These biochemical and morphometric indicators of reproductive status advance the understanding of manatee physiology.