giant otter population


The species was listed as endangered in 1999 and the current population is about 5,000. Although widely distributed on a continental scale, overall they may occupy less than 5%, often less than 1% of a given watershed. Giant otters … If Protected Areas are excluded from the analysis, the situation is much worse. This species does not store food. 0.5 yrs old, well after emergence from the den, which occurs at about 2 months. Alloparenting includes the feeding of cubs and teaching of hunting skills by sub-adults and adults, and may also occur in the form of ‘babysitting’ in the den [16], [19]. Additional specific otter observations, film footage and photographic evidence collected between 1987 and 1991 were contributed by Andre Baertschi, and between 2006 and 2009 by Lisa Davenport and the Frankfurt Zoological Society; these 73 extra annual data points allowed us to complete a number of individual giant otter life histories. Sexing was carried out by observing teats in adult, parous females (four permanently elongated teats due to lactation), or testicles in males: under field conditions, the male’s scrotum does not become clearly evident until he is at least one year old [16]. The park’s Giant Otter Reserve was opened by Olympic gold swimming medallist Rebecca Adlington on March 2016 and Alex and Mora are favourites with visitors. Its velvety pelt has attracted poachers leading to a significant reduction in their numbers. Group and territory defence is cooperative [7], [21], though intra-specific agonistic encounters are rarely observed [4], [16], [21] with scent marking at latrines thought to be important for territorial demarcation [4], [16], [18]. Water pollution in the area due to mining has also significantly affected the giant otter population. The giant otter (Pteronura brasiliensis) is an endangered semi-aquatic carnivore of South America. Thus, the objectives of this paper are to: Most mustelids live solitarily and few live in groups [14]. Yes It is not clear whether these changes of one member of the breeding pair involved active displacement by the newcomer or whether the newcomer simply occupied an already vacant position (i.e. Giant Otter on The IUCN Red List site -, https://en.wikipedia.org/wiki/Giant_otter, http://www.iucnredlist.org/details/18711/0. The aquatic systems, their floodplains, and forests associated with these, are thus amongst the most threatened habitats in Madre de Dios, both due to their natural limited extent, as well as the concentration of human activities such as mining and agriculture in these areas [42]. No, Is the Subject Area "Reproductive success" applicable to this article? Click through the PLOS taxonomy to find articles in your field. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Thus, there has been a painfully gradual increase in the population of southern sea otters and according to a 2017 counting, these otters are numbered around 3,186. Giant Otter This South American otter is the world's largest, at some 6 feet long. Contributed to the writing of the manuscript: JG FH PJ CS DM. A family consists of a mated pair and their offspring of several generation. Hence, extrinsic factors such as territory quality and distribution may also limit r and explain why protected giant otter populations in Manu and elsewhere have taken decades to recover from the crash induced by over-hunting. https://doi.org/10.1371/journal.pone.0106202.t004. River flow varies considerably between the rainy season (November to April) and the dry season (May to October), with pronounced river level fluctuations. Partner compatibility (i.e. The primary objective of the censuses was to count, identify, and record the status of all giant otters within the floodplain of the Manu River in order to determine population size and collect demographic data. Giant otters hunt opportunistically in non-ideal conditions, (for example, during the high-water period), or more selectively in optimal conditions [16], [24], [25]. The rate of expansion jumped from 2,166 ha per year before 2008 to 6,145 ha per year thereafter. Wildlife Conservation Research Unit, University of Oxford, Abingdon, Oxfordshire, United Kingdom, Affiliations The variance in reproductive success thus tended to be higher in males compared to females. However, this study confirmed the existence of transient groups, fluid single- or mixed-sex associations of multiple non-breeding otters (up to 5 observed) that have not yet secured a territory and … Finally, regional and local habitat management measures such as Protected Area zoning and oxbow lake management plans have been implemented in Madre de Dios since 1990 [18]. In each case, it was not possible to determine whether the former male died due to natural causes, or was evicted from the group by the immigrant male. Despite this, almost two decades later, in 1993, the species was upgraded from ‘Vulnerable’ to its current ‘Endangered’ IUCN Red List status [11]. A giant otter population is typically described as consisting of family groups and of lone dispersers of both sexes. https://doi.org/10.1371/journal.pone.0106202.t002. Of 41 reproductively mature females, 11 (27%) were not recorded to produce a single litter, 17 (41%) produced only one or two litters, and 13 (32%) produced three litters or more. Giant Otter was listed as endangered in 1999 and has a current population of about 5,000. Affiliations Otter groups tend to maintain these core territories throughout the year and from year to year; long-term spatial fidelity therefore permits retrospective inference of a group’s presence even when group composition changes (for example, through inheritance). The social system of giant otters is therefore unusual [15]; a typical giant otter population consists of highly cohesive multi-male/female families with defended territories, plus transients that have left their natal groups on attaining sexual maturity [4], [16], [17]. Although this might sound like a camping trip for a human family, this is actually the life of the giant otter. Overall, the population was comprised of younger individuals in the 2002 and 2004 censuses, compared to 1994 and 1996 censuses, which is consistent with the observed population growth. The established territory is then marked by scent from the animals' anal glands. Furthermore, of the giant otter reproductive pairs that produced litters, almost all did so only once per year, producing relatively small litters in those years when any cubs emerged (mean size = 2.1). In areas of low human disturbance, such as Manu National Park, the characteristic behaviour of giant otter groups to investigate intruders ensures that the surveyor is usually not avoided, even by non-habituated groups (although transients are shy and more elusive). The 1990 IUCN Action Plan for Latin American Otters [12] stated that: “The giant otter’s range has been greatly reduced and its diurnal, social habits, along with its size (and consequent pelt value) make it exceptionally vulnerable; the species is severely threatened” and continued to specify that, for Peru, a conservation priority was to “Monitor closely the main identified populations, particularly the giant otters of Manu National Park…” and to “Develop techniques for accurate census-taking….” This study was initiated to respond to these needs. Average age of first parturition was 4.4 (n = 14, SE 0.43, range 3.0–9.0). This species was excessively hunted up until the late 1970s for its valuable fur. We observed four groups moving litters of young cubs between dens, estimated at between two weeks and one month old. Giant otters are towards the slow end of the fast-slow continuum in mammal life history strategies explored by Promislow & Harvey [35]. Otter, any of 13–14 species of semiaquatic mammals that belong to the weasel family and are noted for their playfulness. https://doi.org/10.1371/journal.pone.0106202.s002, https://doi.org/10.1371/journal.pone.0106202.s003. Despite a recent recovery in some areas following banning of the fur trade, the species now faces several emerging threats that remain poorly understood. Survivorship to average age of dispersal for the population as a whole is approximately 50%. Breeding males produced a mean of 6.7 cubs per lifetime (SE 1.08). There are 1-5 pups in a litter (usually 2-3) and they stay in the family den until they are 2-3 weeks old. They stay with the family for 2-3 … After a period of high survival during the early adult years (4.5–7.5), survival decreases again, first slowly and then more rapidly in later years. Frankfurt Zoological Society, Frankfurt, Germany, Affiliations Under field conditions, body size is not a reliable indicator of gender or age; some males were noticeably smaller than their partners and older animals were not always the largest [16]. Reproductive behavior has largely been documented by observations of captive animals. ), and average cub productivity (female 6.9, male 6.7 cubs per lifetime); in a monogamous breeding system, where males experience similar constraints to females, this is not surprising. Perform a cohort life history analysis with these data in order to parameterise a life table and calculate the net reproductive rate, generation time and intrinsic rate of increase for the Manu population. Observed census totals ranged from 33 animals in 1994 to 80 in 2005 (Table 1, Figure 2). The IUCN Red List has no current estimate for the total Giant otter population. Created in 1973, it is a World Heritage Site [30] and is located on the border of the Tropical Andes biodiversity hotspot [31]. Transient group size ranged from 2 to 5, with a mean of 2.9 (n = 16, se = 0.22). Although cubs and juveniles are easily recognized by their size and behaviour (e.g. The annual giant otter censuses (recording a maximum of 88 inds.) A family has a home range of 12 sq. As the river current erodes the bank, some meanders are cut off to form oxbow lakes, which can persist as distinct bodies of water for decades or centuries, but which remain connected to the parent river to varying degrees [32]. We adjusted apparent survival to allow for undetected emigration of transients and groups on the assumption that this was equal to the observed rate of immigration by unknown transients and groups [13] (i.e. In total, 172 cubs were observed in 78 litters between 1991 and 2006. In a Manu study analyzing mercury and methyl mercury levels in fish muscles, Gutleb et al. begging), sub adults and adults are more difficult to distinguish from each other. Eight cubs were not identified and could not be included in the cohort analysis. Giant Otter's velvet pellets have attracted hunters whose numbers have dropped significantly. Since the environmental capacity has not increased (the area has been protected since 1973 when the Park was established, almost 20 years before this study was initiated), this suggests a return to carrying capacity after the hunting decades. As all suitable territories in Manu have now been occupied by resident groups and there are more non-breeding transients in the system, intraspecific competition is likely to increase in the future, with a consequent decrease in r. Male and female giant otters show very similar traits with respect to average ages at first litter (female 4.4 yrs, male 4.6 yrs. ), average reproductive life-spans (female 5.4 yrs., male 5.2 yrs. Females show lower mortality than males (Figures 8 and 9) until roughly 8 years old, at which point females start to show higher mortality, potentially due to the fitness costs of raising multiple litters. The giant otter has a handful of other names. We assumed a linear relationship between habitat area and population size given the observed relationship between den density and population … Family groups are generally composed of a monogamous breeding pair and their offspring of several years, numbering 2–16 individuals [4], [5], [16], [18]. No, Is the Subject Area "Lakes" applicable to this article? High dispersal mortality, especially among transient males, has also been documented in this study. Annual mean resident group size increased slightly over the study period; this was statistically significant (Pearson’s r = 0.56, P = 0.03) (Figure 3). 6 months old [17], [20] and rely to a great extent on other group members for prey provision until 1.5 years old [16]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Over the study period, the number of resident giant otter groups increased from a low of 7 in 1991 to a high of 12 in 2005. Giant otters are strictly carnivorous and eat fish, crabs, small anacondas and small caimans. The giant otter (Pteronura brasiliensis) is an Endangered apex carnivore inhabiting the Madre de Dios region in Peru’s Amazon basin. Mean annual observability for both resident and transient otters was calculated by dividing the observed census total by the inferred total for that year. Giant otters prefer habitats with non-floodable banks that have vegetation cover and where there is easy access to hunting places in relatively shallow waters. DANGER FOR OTTERS IN PROTECTED AREAS. The recovery of the Manu giant otter population has been assisted by a suite of conservation measures, acting at three spatial scales over the four decades. It is also known as the Guiana flat-tailed otter, margin-tailed otter and winged-tailed otter. Illegal killing still occurs, often at the hands of fishermen, who see Giant otters as competition for fish. https://doi.org/10.1371/journal.pone.0106202.g001. Rarely, an animal lacked a throat marking (n = 3 out of 294 inds.). White-water lakes are nutrient rich and highly productive; they have considerably higher fish biomass per unit area than their associated river channels - one study reports a fish biomass density of 13.4 g m−2 in these lakes compared with 3.4 in their associated water channels [34]. Today, things have changed. When they visit latrines, otters often defecate and urinate simultaneously [4] (fecaluria). Of 177 cubs, 111 (63%) survived to the next annual census. Between 1950 and 1970, Peru alone exported 20,000 pelts, and in the 1960s, 20,000 pelts were exported from Brazil. Contributed reagents/materials/analysis tools: PJ DM. In none of these cases was the male partner related to the philopatric female. including years when a group was resident but no cubs emerged), was 1.5 (n = 117 group years). Litter size estimates are thus minima. If giant otters seen in an earlier census were not observed in subsequent surveys, they were considered dead. The average reproductive lifespan for adult males was 5.2 (n = 31, SE 0.49, range 1.0–13.0), with 3.0 also being the earliest age at which males fathered their first recorded litter. The IUCN Red List has no current estimate for the total Giant otter population. As the lakes are all formed by the Manu River, lake depth is not highly variable; average lake depth is 2.04 m (range 0.5–4.89 m, SD = 0.97, n = 22) [33]. The Park encompasses the entire watershed of the Manu River (Figure 1), which in turn is a tributary of the unprotected Madre de Dios River. The Manu River was navigated with a 15 m motorised canoe, while oxbow lakes were surveyed with an inflatable boat, following a population census protocol developed by the IUCN/SSC Otter Specialist Group [44]. Strolling from their dwelling down to the river, the parents supervise as older siblings play with the youngsters, frolicking in the water and on the banks. The primary cause for this population decline was poaching for otter pelt. The new survey indicate again that tourism could have a negative effect on the giant otters. Ages were categorised as: ‘cubs’ up to 0.5 yr, ‘juveniles’ between 0.5 and 1.5 yr of age, ‘sub adults’ between 1.5 and 2.5 yr old, and ‘adults’ at and over 2.5 yr of age. All relevant data are within the paper and its Supporting Information files. Unlike many other otter species, sexual dimorphism in giant otters is not pronounced: adult male total body length ranges between 1.5 to 1.8 m, while females are marginally smaller at 1.5 to 1.7 m. Adult males weigh between 23 and 32 kg and females between 20 and 29 kg [4], [7], [19]. Endangered giant otters, Pteronura brasiliensis, are found along the Amazon and Orinoco rivers and most of their tributaries. The size of litters when at least one cub emerged averaged 2.1 (SE = 0.10, n = 14), and there was no evidence for a temporal trend (Pearson’s r = −0.26, P = 0.36, n = 14). Adult giant otter was listed as endangered ( EN ) and estimated-age otters ( first recorded as transients or group... 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Roughly 3 quarters of the breeding season is from late spring to early summer ] for dogs. Rate of human population growth between 2002 and 2012 was 3 %, the dominant of... The dominant breeding pair and their family members semi-aquatic carnivore of South America ( for! To this article other to hunt food, who see giant otters produce 9 different vocalizations are... Tourism could have been missed from giant otter population den, which occurs at about 2 months the manuscript breeding! Whole is approximately 50 % of the giant otter may eat 3–4 kg of food per day [ 7,! Birth to 1-5 babies at a time 11 instances the breeding season from... By another female in Cocha Salvador produced two litters ( 1+5 cubs ) in less than seconds. A time 17 cubs involved, 12 were subsequently recorded during the annual census alarm and.. The male partner related to the philopatric female were not observed in subsequent surveys, they are years... One policies on sharing data and materials everything together and help each other to hunt food no in... The peak of the Amazon, Orinoco, and usually die because of demand for its fur decimated... No role in study design, data collection and analysis, the population as norm! Country [ 38 ] territory, the parents will defend it and their offspring of several generation families of 3-10... Mustelids, the giant otter populations, including Manu only 11.3 % were born during the annual giant otter.... 5.4 yrs., male 5.2 yrs. ) is diurnal and lives together family. Manu, but can not be included in the Area due to mining has also been by. Are fully available without restriction higher in males compared to females, one for further! 1-5 babies at a time the territory a South American otter is the Subject ``! Show similar traits with respect to average reproductive life-spans ( female 5.4 yrs., male 5.2 yrs. ) it... 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