Trichechus Inunguis Research Articles

STANDARD OF MEASUREMENT AMONG LOCAL INHABITANTS IN THE MIDDLE SOLIMÕES, OCCIDENTAL AMAZONIA, AND ITS USE IN MORPHOMETRICS OF AMAZONIAN MANATEE (<i>Trichechus inunguis<i/> NATTERER, 1883)

This study analyzed measurements of Amazonian manatees taken by local people on the middle Solimoes river, converting the length of the inch of local people to the metric system, and verifying the existence of a difference between the value of local men´s inch in metric scale and the international metric standards for the measurement. Field trips were taken to the Mamiraua and Amana reserves, in Central Amazonia, to confirm the use of the inch as a measurement unit. Interviews were applied and the inches of 508 adult males resident in the town of Tefe and in the Mamiraua and Amana reserves were measured. The sample consisted of persons whose experience with manatee capture ranged from three to 43 years. The average value for the local inhabitant inch was 21.71 cm. A Student’s t-test applied to the result demonstrated a highly significant difference in relation to the value of the inch described in the literature. The use of morphometric data contributed by local people, in growth studies of Amazonian manatees must weigh the value of 21.71 cm in the conversion of the local´s inch to the metric scale, considering an error of 0.05 cm for each converted inch measure.

Single nucleotide polymorphisms from cytochrome b gene as a useful protocol in forensic genetics against the illegal hunting of manatees: Trichechus manatus, Trichechus inunguis, Trichechus senegalensis, and Dugong dugon (Eutheria: Sirenia)

The identification of mitochondrial DNA polymorphisms is one of the most efficient methods for species differentiation. Genotyping of molecular markers using PCR/RFLP is a reliable, sensitive and inexpensive method for the detection of species specific mutations. The major causes of decline in Sirenia populations are accidental and intentional catches, collisions with boats and habitat loss. The goal of the present study was to identify, in silico, nucleotide mutations in the cytochrome b gene that can be used for the future development of forensic tools capable of using small tissue fragments to discriminate manatee meat from domesticated species meat commonly used as food sources (bovine, ovine, caprine and swine). DNA sequence alignments revealed two polymorphic sites distinguishing the manatee species from domestic species. The present study reinforced the power of cytochrome polymorphisms as powerful markers for species identification, which may be particularly useful for identifying vulnerable/endangered species. The data provided herein also suggest such mtDNA markers as important conservation tools for combating predatory manatee hunting for illegal meat trade in the Americas

156 MONITORING SALIVARY TESTOSTERONE CONCENTRATIONS FROM CAPTIVE AMAZONIAN MANATEES (TRICHECHUS INUNGUIS): IS THERE SEASONAL PATTERN?

Seasonality of reproduction in many nondomestic animal species appears to represent an accommodation to environmental variables, as food availability, in which influence reproductive success. Males can show a decrease of testicular size, sperm concentration, and serum concentration of testosterone because of food restriction. The Amazonian manatee (Trichechus inunguis, Mammalia: Sirenia) is a threatened aquatic mammal, endemic of the Amazon basin (South America), and is the only sirenian that occurs exclusively in fresh water. Although information is lacking about the reproductive endocrinology of free-ranging T. inunguis, they are considered seasonal breeders, with copulation and births occurring between December and July, coinciding with the increase in Amazon basin water levels and the period of most availability of food for the species (Best 1982 Biotropica 14, 76–78). Salivary steroid measurement is a noninvasive way to monitor steroid concentration, which is well correlated with the level of steroids in the serum. The aim of this study was to verify if testosterone concentrations of male T. inunguis kept in captivity, without variation of food availability, show a seasonal pattern. Were used 4 adult male Amazonian manatees kept in captivity in the Laboratory of Aquatic Mammals of the National Institute of Amazonian Research–LMA/INPA, Brazil. They were fed all year with paragrass and vegetables, at not less than 8% of body weight per day. For sample collection, the pool was drained and saliva was collected from mouth mucosa using a metal spoon. Samples were collected weekly for 12 weeks in 2 periods (March–June and September–November). Salivary testosterone was measured by RIA for total testosterone using an adapted protocol previously validated for the species (Amaral et al. 2009 J. Zoo Wildl. Med. 40, 458–465) The data were analysed in a 3 × 2 factorial design, where the factors were month (each 4 weeks = 1 month) and period, using GLM test for repeated-measures. The means of salivary androgen levels were 28.80 ± 18.56 pg mL–1 and 30.77 ± 16.76 pg mL–1 for first and second periods, respectively. There were no significant main effects of month (P = 0.454), period (P = 0.607), or interaction between factors (P = 0.635). These results suggest that captive male Amazonian manatees apparently do not show reproductive seasonality. However, it is recommended to verify the existence of variation in testicular size and sperm concentration. This finding is important information for the future reproductive management of captive Amazonian manatee. The authors thank PREVET staff for help with the samples collection, and FAPESP (2008/05760-5), CNPq (Universal 475596/2009-9), Petrobras Ambiental (Projeto Mamíferos Aquáticos da Amazônia: Conservação e Pesquisa), and AMPA for the financial support.

Body weight/length relationship and mass estimation using morphometric measurements in Amazonian manatees Trichechus inunguis (Mammalia: Sirenia)

This study defined the body weight/length relationship and an equation for body mass estimation using morphometric measurements on Amazonian manatees Trichechus inunguis (Mammalia: Sirenia). Total length (TL), maximum girth (MG) and body mass (M) were obtained from 91 captive Amazonian manatees (46 males and 45 females) of different ages, and TL and M were obtained from eight free-ranging Amazonian manatees (6 males and 2 females). The data were analysed by linear and multiple linear regressions. The maximum length and mass measured were 266.5 cm and 379.5 kg, respectively. The equation for body weight/length relationship was M = 0.00001070 * TL3.122 (r2 = 0.984) (Equation I) and no differences between sexes and between captive and free-ranging animals were found (P > 0.05). We calculated two more equations for mass estimation (Equation II: M = 0.00003284 * TL1.857 * MG1.106, r2 = 0.992; and Equation III: M = 1.506 + 0.00003477 * TL * MG2, r2 = 0.995), and the best equation (high correlation coefficient and low percentage of residues) was Equation III. Equation I provides the body condition of manatees, whereas Equation III is more accurate for estimating body mass. Both equations are important tools for management of captive and free-ranging Amazonian manatees.

Growth curve of free-ranging Trichechus inunguis

The objective of this work was to describe growth curves for free-ranging Amazonian manatees in Brazil. Data analyzed included age estimates and biometrics from 60 Amazonian manatees (33 males and 27 females) captured between 1993 and 2006 by local residents of the mid-Solimões and Pirativa Rivers, in Amazonia, and collected by the Instituto de Desenvolvimento Sustentável Mamirauá and Centro Nacional de Conservação e Manejo de Mamíferos Aquáticos/ICMBio. The non-linear mathematical model used to analyze the data was the von Bertalanffy's equation; two growth curves were calculated, one for males L(t)male = 299.4[1-e-0.0897507(t+6.55696)], and one for females L(t)female = 256.1[1-e-0.23731(t+ 3.01921)]. Based on these equations, length at birth for the Amazonian manatee is estimated at 133.2 cm (average = 113.0 cm; SD = 34.4 cm) for males, and 131.0 cm (average = 124.7 cm; SD = 22.0 cm) for females. Among the males, the annual growth rate was 0.09 cm (95% CI: ± 0.002), with a maximum length of 299.4 cm (95% CI: ± 2.039), while females presented a growth rate of 0.24 cm per year (95% CI: ± 0.004), reaching up to 256.1 cm (95% CI: ± 0.4832) of total length. Even though von Bertalanffy's equation is not commonly used for sirenians, and considering that when previously applied it did not obtain satisfactory results, in this study it proved adequate for the establishment of the growth curve for free-ranging Amazonian manatees.

Urinary parameters of Trichechus inunguis (Mammalia, Sirenia): reference values for the Amazonian Manatee

The Amazonian manatee, Trichechus inunguis (Natterer 1883) is endemic to the Amazon Basin and is currently considered a vulnerable species. In order to establish normality ranges of urinary parameters to help monitor the health of this species in captivity, chemical urinalyses were performed on twelve males and nine females of various age groups. Urine was collected once a month for twelve months in the tanks just after being drained, by placing stainless steel containers under the genital slit of females and applying abdominal massages to males in order to stimulate urination. Quantitative data of glucose, urea, creatinine, uric acid and amylase levels were obtained using colorimetric spectrophotometry. Dip strips were also useful for routine analyses, despite only providing qualitative results. Normal range to glucose levels, regardless of sex or age class, was 3.0 to 3.6 mgxdL-1, coinciding with qualitative values of glucose measured by dip strips. Statistical differences observed in some parameter levels suggest that some urine parameters analysed must take into consideration the sex and the age class of the animal studied, being these differences less remarkable in creatinine and amylase levels. To this last one, statistical difference was detected only in the calve's urine (7.0 to 11.5 mgxdL-1) compared to other age classes samples (4.1 to 5.3 mgxdL-1). The results presented here may be used as comparative data in future research on urinalysis in related species.

Estado del manatí del Amazonas <em>(Trichechus inunguis)</em> en la Reserva Cuyabeno, Ecuador

Los manatíes amazónicos viven en ríos de aguas negras y lagunas de la Cuenca Amazónica. La primera información sobre la distribución y el estado de conservación de manatíes en la Reserva Cuyabeno proviene de un estudio realizado en 1983 por Timm y otros [1]. Ellos concluyeron que el manatí se puede extinguir en la próxima década. En este artículo se presenta los resultados de observaciones y entrevistas realizados desde 1996 a 1999, trece años después. Durante 127 días de monitoreo del Delfín Amazónico (Inia geoffrensis) en el habitat del manatí a lo largo de ríos y lagunas de agua negra, se observó durante 456 horas. Adicionalmente se realizaron monitoreos dirigidos a manatíes en las Lagunas Grandes de Cuyabeno. Entrevistas con guías de turismo, guardaparques e indígenas dan una lista completa de avistamientos de manatíes, su distribución y la situación de conservación. La abundancia relativa estimada en el Río Cuyabeno es de 0,01 animales/hora de esfuerzo y aün menor en el río Lagartococha con 0,007 animales/ hora de esfuerzo. Las poblaciones en el rio Lagartococha parecen severamente reducidas. En ambos ríos la caza entre 1995 y 1998 continuó. A pesar de la protección legal se mataron al menos 16 animales dentro de la Reserva Cuyabeno, por ende el hecho de vivir en una area protegida no necesariamente significa la sobrevivencia de la especie.

The lesser of two evils: seasonal migrations of Amazonian manatees in the Western Amazon

We investigated the paradox of why Amazonian manatees Trichechus inunguis undergo seasonal migrations to a habitat where they apparently fast. Ten males were tracked using VHF telemetry between 1994 and 2006 in the Mamiraua and Amana Sustainable Development Reserves, constituting the only long-term dataset on Amazonian manatee movements in the wild. Their habitat was characterized by analysing aquatic space and macrophyte coverage dynamics associated with the annual flood-pulse cycle of the River Solimoes. Habitat information came from fieldwork, two hydrographs, a three-dimensional model of the water bodies and classifications of Landsat-TM/ETM+ images. We show that during high-water season (mid-May to end-June), males stay in varzea lakes in association with macrophytes, which they select. We then show that, during low-water (October–November), the drastic reduction in aquatic space in the varzea leads to the risk of their habitat drying out and increases the manatees' vulnerability to predators such as caimans, jaguars and humans. This explains why males migrate to Ria Amana. Based on data on illegal hunting, we argue that this habitat variability influences females to migrate too. We then use published knowledge of the environment's dynamics to argue that when water levels are high, the habitats that can support the largest manatee populations are the varzeas of white-water rivers, and we conjecture that rias are the species' main low-water refuges throughout Western Amazonia. Finally, we warn that the species may be at greater risk than previously thought, because migration and low-water levels make manatees particularly vulnerable to hunters. Moreover, because the flooding regime of Amazonian rivers is strongly related to large-scale climatic phenomena, there might be a perilous connection between climate change and the future prospects for the species. Our experience reveals that the success of research and conservation of wild Amazonian manatees depends on close working relationships with local inhabitants

Morphology, morphometry and ultrastructure of the Amazonian manatee (Sirenia: Trichechidae) spermatozoa

This study describes the morphological, morphometric and ultrastructural characteristics of the Amazonian manatee Trichechus inunguis (Natterer, 1883) spermatozoon. The spermatozoa were obtained from a urine sample of an adult T. inunguis kept in captivity. The spermatozoa were analyzed by light and transmission electron microscopy. The head of Amazonian manatee spermatozoa had a flat oval shape and a well distinguishable midpiece. The mean dimensions of the spermatozoa were: head length, 7.49 ± 0.24 µm; head width, 3.53 ± 0.19 µm; head thickness, 1.61 ± 0.13 µm; midpiece length, 11.36 ± 0.34 µm; flagellum length, 40.91 ± 1.94 µm; total tail length, 52.16 ± 1.06 µm; total spermatozoon length, 60.08 ± 1.40 µm. The Amazonian manatee spermatozoa were similar in shape to other sirenian spermatozoa; however, presenting a different size. This study describes, for the first time, the morphometric and ultrastructural characteristics of the Amazonian manatee spermatozoa, and also demonstrates the possible use of spermatozoa retrieved from urine samples for biological studies.

Noninvasive Monitoring of Androgens in Male Amazonian Manatee (Trichechus inunguis): Biologic Validation

The Amazonian manatee (Trichechus inunguis) is endemic in the Amazonian basin and is the only exclusively fresh water sirenian. Historically hunted on a large scale, this species is now considered endangered, and studies on the reproductive physiology are critical for the improvement of reproductive management of captive and wild populations of manatees. The aim of this study was to verify the viability of androgen measurement in saliva, lacrimal, urine, and fecal samples of the Amazonian manatee by conducting a hormone challenge. Two adult male manatees (A-1 and A-2) were submitted to an experimentation protocol of 12 day (D1 to D10). On D0, the animals received an intramuscular injection of gonadotropin-releasing hormone (GnRH)-analogue. Salivary, lacrimal, urinary, and fecal samples were collected daily (between 0800 hours and 0900 hours) and frozen at -20 degrees C until assayed. Fecal samples were lyophilized, extracted with 80% methanol, and diluted in buffer before the radioimmunoassay (RIA). Urine samples underwent acid hydrolysis and were diluted in depleted bovine serum. Salivary and lacrimal samples were assayed without the extraction step. Hormonal assays were conducted with a commercial testosterone RIA kit. An androgen peak (> median + 2 interquartile range [IQR]) was observed in all matrices of both animals, although it was less prominent in the lacrimal samples of A-2. However, the fecal androgen peak (A-1 peak = 293.78 ng/g dry feces, median [IQR] = 143.58 [32.38] ng/g dry feces; A-2 peak = 686.72 ng/g dry feces, median [IQR] = 243.82 [193.16] ng/g dry feces) occurred later than urinary (A-1 peak = 648.16 ng/mg creatinine [Cr], median [IQR] = 23.88 [30.44] ng/mg Cr; A-2 peak = 370.44 ng/mg Cr, median [IQR] = 113.87 [117.73] ng/mg Cr) and salivary (A-1 peak = 678.89 pg/ml, median [IQR] = 103.69 [119.86] pg/ml; A-2 peak = 733.71 pg/ml, median [IQR] = 262.92 [211.44] pg/ml) androgen peaks. These intervals appear to be correlated with the long digesta passage time in this species. The salivary and urinary peaks were closely associated. These results demonstrate that androgen concentrations in saliva, urine, or feces samples reflect reliably physiologic events and are a powerful tool for noninvasive reproductive monitoring of Amazonian manatees.

Reproductive Anatomy of the Female Amazonian Manatee Trichechus inunguis Natterer, 1883 (Mammalia: Sirenia)

The Amazonian manatee (Trichechus inunguis) is uniparous and has a slow reproduction cycle due to a long gestation period and long interval between births. Even though protected by law, hunting remains one of the main causes hindering the natural population growth of this species in the wild. The histology and reproductive anatomy provide information on the history and reproductive status of the female and offer a tool for the conservation of the species. The present study describes the anatomy of the female reproductive tract in T. inunguis. It is based on materials from three reproductive tracts fixed in 10% buffered formalin. The ovaries, uterine tubes, uterus, vagina, and external genitalia are described. The hymen presents two tiny openings separated by a segment that, upon rupturing during the first copulation, should make up a single vaginal opening. A still intact hymen and the absence of placental scars in the uterus were found in one specimen. Additionally, the presence of a hemorrhagic body and Graafian follicles on the right ovary were observed, as well as whitish scars and among them, possible corpora albicantia. These findings suggest that T. inunguis undergoes infertile estrus cycles before its first gestation. Macroscopically, counting of the whitish scars is hindered by the small diameter of these structures. It is not possible to differentiate between the scars resulting from ruptured (corpora albicantia) and nonruptured follicles (regressed corpora atretica). The presence of whitish scars on both ovaries of the same specimen suggests their bilateral function in T. inunguis.

Placentation in the Amazonian manatee (Trichechus inunguis)

Evidence from several sources supports a close phylogenetic relationship between elephants and sirenians. To explore whether this was reflected in similar placentation, we examined eight delivered placentae from the Amazonian manatee using light microscopy and immunohistochemistry. In addition, the fetal placental circulation was described by scanning electron microscopy of vessel casts. The manatee placenta was zonary and endotheliochorial, like that of the elephant. The interhaemal barrier comprised maternal endothelium, cytotrophoblasts and fetal endothelium. We found columnar trophoblast beneath the chorionic plate and lining lacunae in this region, but there was no trace in the term placenta of haemophagous activity. The gross anatomy of the cord and fetal membranes was consistent with previous descriptions and included a four-chambered allantoic sac, as also found in the elephant and other afrotherians. Connective tissue septae descended from the chorionic plate and carried blood vessels to the labyrinth, where they gave rise to a dense capillary network. This appeared to drain into shorter vessels near the chorionic plate. The maternal vasculature could not be examined in the same detail, but maternal capillaries ran rather straight and roughly parallel to the fetal ones. Overall, there is a close resemblance in placentation between the manatee and the elephant.

Diet induced differences in carbon isotope fractionation between sirenians and terrestrial ungulates

Carbon isotope differences (Δ13C) between bioapatite and diet, collagen and diet, and bioapatite and collagen were calculated for four species of sirenians, Dugong dugon (Muller), Trichechus manatus (Linnaeus), Trichechus inunguis (Natterer), and the extinct Hydrodamalis gigas (Zimmerman). Bone and tooth samples were taken from archived materials collected from populations during the mid eighteenth century (H. gigas), between 1978 and 1984 (T. manatus, T. inunguis), and between 1997 and 1999 (D. dugon). Mean Δ13C values were compared with those for terrestrial ungulates, carnivores, and six species of carnivorous marine mammals (cetaceans = 1; pinnipeds = 4; mustelids = 1). Significant differences in mean δ13C values among species for all tissue types were detected that separated species or populations foraging on freshwater plants or attached marine macroalgae (δ13C values −4‰; Δ13Cbioapatite–diet ∼11‰). Likewise, Δ13Cbioapatite–collagen values for freshwater and algal-foraging species (∼7‰) were greater than those for seagrass-foraging species (∼5‰). Variation in Δ13C values calculated between tissues and between tissues and diet among species may relate to the nutritional composition of a species’ diet and the extent and type of microbial fermentation that occurs during digestion of different types of plants. These results highlight the complications that can arise when making dietary interpretations without having first determined species-specific Δ13Ctissue–diet values.

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

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

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

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

Orofacial morphology and feeding behaviour of the dugong, Amazonian, West African and Antillean manatees (Mammalia: Sirenia): functional morphology of the muscular‐vibrissal complex

AbstractThe external orofacial morphology, perioral bristle distribution and feeding behaviour of Dugong dugon, Trichechus inunguis, T. senegalensis and T. manatus are described. Despite their differing orofacial morphology, dugongs and trichechids possess six similar regions: the oral disk, orofacial ridge, supradisk, chin and upper and lower bristle (modified vibrissae) pads. All living sirenians possess six discrete fields of bristles: four on the upper lip (U1, U2, U3, and U4) and two on the lower lip (L1 and L2). The distribution of these fields is similar among all living sirenians with the exception of the U1 bristle fields in dugongs. Perioral bristle field boundaries are distinguished by distinct changes in their length‐to‐diameter ratios. Both dugongs and trichechids possess bristle‐like hairs covering the oral disk, which possess length‐to‐diameter ratios intermediate between perioral bristles and postcranial hairs. Sirenians use elaborated facial musculature in conjunction with perioral bristles to acquire, manipulate and ingest aquatic vegetation. The U2 and L1 fields are the primary bristles used to ingest vegetation. The use of the L1 bristle fields is similar among all living sirenians. However, dugongs and trichechids are divergent in their use of the U1 and U2 bristle fields. Dugongs use the U2 bristles fields in a medial‐to‐lateral motion, while all trichechids use the U2 bristles in a prehensile, lateral‐to‐medial, grasping motion. These divergent behaviours presumably allow dugongs to exploit benthic foraging (i.e. consumption of rhizomes) to a greater degree than trichechids. Functional hypotheses of rhizome excavation are presented for both dugongs and trichechids.

Food Plants Eaten by Amazonian Manatees (Trichechus inunguis, Mammalia : Sirenia)

To determine the feeding habits of the Amazonian manatee Trichechus inunguis in some Central Amazonian rivers and lakes, we compared plant epidermis found in the stomach contents and/or faeces of animals with a reference collection of plants present in the studied areas. Twenty five samples from digestive tracts of animals found dead and 25 faeces samples found floating were analyzed. From these samples, 24 aquatic macrophytes were identified. The Gramineae family was identified in 96% of the samples, Paspalum repens and Echinochloa polystachya being the most abundant in the samples. The second most frequent family was the Pontederiaceae primarily Eichhornia crassipes. During the high water period, the animals showed a more selective diet (eight identified species). In the low water period, when food was more scarce, the animals showed a larger diversity of species in their diet (21 species of plants). Differences in the diet among the two studied areas reflected the physiographics characteristics of the region. Amazonian manatees fed mostly on emergent plants.

Signature information and individual recognition in the isolation calls of Amazonian manatees, Trichechus inunguis (Mammalia: Sirenia)

Acoustic signals are assumed to form the basis of manatee communication. Empirical evidence of individual vocal recognition has been reported. If manatees can recognize one another by acoustical means, it should be possible to identify individual vocal patterns. We recorded vocalizations of 14 individually housed Amazonian manatees and then digitized selected vocalizations, allowing seven variables to be measured and subjected to multivariate statistical treatment. Discriminant function analysis indicated that individuals can be separated on the basis of variables related to the fundamental frequency and signal duration. We observed significant differences in the vocal patterns between sexes and age classes. Females tended to have greater fundamental frequency and shorter note duration than males. Calves had shorter note durations and greater values for the fundamental frequency range than subadults and adults. An inverse relationship between total body length and fundamental frequency range suggests that the fundamental frequency becomes more defined as the animal ages. The similar individual patterns in the vocalizations of a mother and calf pair are discussed. Individual recognition by Amazonian manatees according to their vocal patterns is suggested through a preliminary playback experiment.

Lack of species-specific vocal recognition in Amazonian manatees: Trichechus inunguis

Playback experiments were conducted in order to test for the existence of species-specific vocal recognition in Amazonian manatees. The animals were isolated in pools while acoustic stimuli were played from a tape recorder and transmitted underwater through a loudspeaker. Nine animals were monitored for response to playback vocalizations from eighteen different individuals, nine from each species (Trichechus inunguis and T. manatus manatus). No significant differences were detected in the response of manatees exposed to the different stimuli. Only the time spent close to the speaker was greater when the animals were exposed to conspecific vocalizations (ρ=0.375). This result suggests that Amazonian manatees cannot recognize differences between their own and another manatee species’ vocalization. The methodology was also tested and no difference in the response of animals exposed to silence or to tape hiss (blank tape used as control) was found. Testing the response to the presence or absence of vocalizations, significant differences were found in time elapsed between the playback and the response (ρ<0.001) and in the time spent next to the speaker (ρ=0.032), confirming their great ability to perceive sounds underwater. [Work supported by FBPN, MacArthur Foundation, CI, FINEP, MCT/PPG7 and CNPq.]

Seasonal variations in blood parameters of the Amazonian manatee, Trichechus inunguis

Seasonal variations in body weight, food consumption and blood glucose, total lipids, urea, total proteins, albumin and globulins of captive Amazonian manatees, Trichechus inunguis, were determined. Body weight changed significantly along the year, increasing from autumn to spring and decreasing in summer. The mean daily food intake of paragrass remained almost unchanged along the year. Paragrass administered to the manatees showed important variations in crude protein and lipid content along the year. No significant differences in blood parameters were registered between males and females in all seasons. Further, there were no significant differences in blood total proteins, albumin and globulins along the year. On the other hand, significant differences in the mean blood glucose, lipids and urea were registered. An increase in the blood glucose in the spring and summer was observed. Blood urea and lipids levels were positively related to paragrass protein and lipids content. These two correlations suggested that these blood parameters are good indicators of the animal nutritional status in the Amazonian manatee.