AMAZONIAN MANATEES (Trichechus inunguis) INHABITING AN EQUATORIAL METROPOLIS: HISTORICAL RECORDS AND MATING ACTIVITY NEAR BELÉM, NORTHERN BRAZIL

The West Indian manatee Trichechus manatus Linnaeus, 1758 and the Amazonian manatee T. inunguis (Natterer, 1883) occur in the Marajó Bay area and in the inlets and channels near Belém. The Amazon Aquatic Mammal Study Group (GEMAM) coordinates a collaborative network for trapped and rescued manatees along the coast of the state of Pará and in the interior of Belém. The presence of the Amazonian manatee is confirmed with the rescue and sightings in the great Belém area. The samples of these manatees are housed in collections of institutions such as MPEG and ICMBio, CMA. On October 31st 2021, Amazonian manatees were sighted swimming near a beach in the Mosqueiro district, in greater Belém. Residents and tourists took images that show a mating behavior reported in the literature for Trichechus spp. The waters in this area are turbid and these records are a significant opportunity to understand this behavior. The event may suggest that Amazonian manatees are returning to the Belém area and its surroundings, as well as to the east coast of the state of Pará, possibly due to the synergic effects of SARS-CoV-2, providing areas less disturbed by humans, pandemic and the current climate change scenario, which would be a hope for this endangered species.


INTRODUCTION
Amazonian manatees (Trichechus inunguis) (Natterer, 1883) are endemic to the Amazon River Basin, distributed from river headwaters in Colombia, Peru and Ecuador up to Marajó Island, in Brazil (Best, 1984). Manatee records for the Brazilian state of Pará date back to the first centuries following Brazil's discovery, always comprising hunting reports until the mid-19th century, indicating great abundance of these aquatic mammals (Vieira & Brito, 2017). Subsistence hunting records are also noted for the Amazon basin and the northern coast of Brazil in the 2000s (Luna et al. 2000;Luna et al., 2008a).
The study conducted by Luna et al. (2008b;2008c) based on interviews describes the occurrence of Trichechus manatus Linnaeus, 1758 and T. inunguis (Natterer, 1883) on Marajó island and the left side of Marajó Bay. In that respect, the non-governmental organization (NGO) Bicho D'água Institute, alongside the Museu Paraense Emílio Goeldi (MPEG), the Fundação Oswaldo Cruz (Fiocruz) and the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), have been carrying out conservation efforts for these animals in the state of Pará, seeking to record occurrence areas and threats. When necessary, these institutions have also contributed to the rescue and rehabilitation of stranded and entangled manatees, aiding in their conservation and proposing public policies for the region.
Currently, four T. inunguis specimens sampled in the vicinities of Belém are housed at the Pará Museu Paraense Emílio Goeldi, obtained at the mouth of Igarapé Tucunduba, Guamá River (MPEG 11298), Icoaraci (MPEG 1518), Abaetetuba (MPEG 42148) and Arapiranga Island (collection number not available). In addition, a young male T. inunguis was recorded as caught by a small gillnet set off Furo das Marinhas, in Santa Bárbara do Pará, on 23 rd June 2017. It survived the event and after a short rehabilitation period in Belém, was released at the same spot where it was found. He was named Tito, and his field number is GEMAM 748 (after the Amazon Aquatic Mammal Study Group, Grupo de Estudos de Mamíferos Aquáticos da Amazônia -GEMAM/MPEG).
Since November 2005, the GEMAM coordinates a collaborative network of investigators and volunteers to search for stranded and liverescued manatees along the Pará state coastline, including Marajó Bay, Eastern Pará state coast and inland Belém area. As a result, GEMAM was informed on October 31 st 2021, of a group of manatees sighted by locals and tourists swimming close to a beach sand strip named Praia do Bispo, in the district of Mosqueiro, Belém (Figure 1). The group of manatees was observed for approximately 60 minutes while filmed by hundreds of voyeurs, as they were reported by locals as being on a 'honeymoon' or 'in great love'. The group of manatees were described as 'a ball of tails and heads water-rolling'. In fact, the filming depicts a typic 'manatee ball', a mating behavior reported in the literature for Trichechus spp. (Hartman, 1979) by three supposedly adult manatees, who were presenting typical courtship behavior ( Figure  2). It should be noted that this conduct has been previously reported for Amazonian manatees (Carvalho et al., 2017). Interestingly, the manatees did not show any distress behavior during their activity although people crowded the beach to observe such an unusual scene. Best (1982) reported that temporary aggregations of Amazonian manatees can occur during the dry season, the alleged reproductive period. The mating system is of the promiscuous type, although there are strategies such as guarding a male to prevent access by other males to the female in estrus (Berta et al., 2006).
The Antillean manatee is also promiscuous and forms mating groups composed of a female in heat and several adult males, creating a reproductive aggregation that can last from a week to a month. During the cycle, the female mates with several males (Reynolds III et al., 2004).
The videos, widely publicized in the local and national media, clearly suggest that mating took place, as one large manatee held the alleged female for more than 2 minutes (Figure 3). The third manatee remained nearby and, at least for several minutes, did not attempt to join/rejoin the group.
Male manatees (Trichechus spp.) can engage in aggressive behavior and competition for receptive females (Hartman, 1979). This is in agreement with the reported behavior known as 'manatee riding' by residents of the Amazon basin (Pereira, 1944). During the same week, professionals from the local Fire Brigade and other Mosqueiro village traders and residents were interviewed by the Bicho D'água team. The interviewees reported that it is not common for manatees to remain so close to the beach at this location, but also that these animals have been seen in the region more frequently in recent years. The firefighters also informed that they believe that the manatees remained during the entire period close to the observing humans because they were 'trapped' in a shallower area due to the low tide. In fact, when the tide came in, they left, moving away from the beach. During the interview, information on manatee feeding areas  was obtained, such as the native vegetation banks that comprise part of the known diet for the species. Regarding their appearance in shallows Mosqueiro waters, Bonvicino et al. (2020) commented that the affluence of the enormous amount of freshwater during the Amazonian rainy season (December-June) may favor the spread of Amazonian manatees throughout the Belém coastline and adjacent islands. This environment provides abundant vegetation for manatee foraging, including Avicennia nitida, Rhizophora mangle, Laguncularia racemosa, Montrichardia arborescens, Spartina brasiliensis, Eichhornia crassipes and Eleocharis interstincta (Best, 1981;Best & Teixeira, 1982;Guterres-Pazin et al., 2014) (Figure 4).
Manatees strongly depend on the local Amazon hydrology, which leads to seasonal increased and decreased river water levels, directly affecting manatee aquatic macrophyte food sources and, consequently, reproduction events (Cantanhede et al., 2004;Arraut et al., 2010). Mosqueiro Island is directly influenced by the Pará River estuary processes, which are governed by the seasonal variability of other river basins, such as the Guamá, that bathes the city of Belém , and local tides. River discharges and tides control two important processes in the estuary, saline intrusion (Rosário et al., 2016) and suspended sediment transport (Carneiro et al., 2020). The tide is characterized by the macrotidal regime at the mouth of the estuary, with amplitudes of 5 meters (Prestes et al., 2017), in the region that comprises Marajó Bay. The tides lose amplitude above the estuary, reaching around 3 meters near Belém (Rosário et al., 2016;DHN, 2021), as well as around Mosqueiro island, becoming a mesotidal regime.
The Pará River estuary region is subjected to two rainfall regimes, where the wet season starts in December going until June, and the drier season occurs from July to January, with peaks between September and November (Moraes et al., 2005). Notably, 2021 was atypically rainy when it was supposed to be a 'normal' dry period (July-November) in the northern coast of Brazil. Heavy rains, in fact, continuously affected Belém during the months of August to November 2021 (INMET, 2021) with a higher freshwater influx to channels and rivers than in a typical' dry period. This is probably due to the current global climate change scenario, which will likely significantly alter rain patterns in the Amazon region, increasing the intensity of extreme precipitation events over western Amazon as a consequence of the increasing total rainfall trends expected for this area (Alves & Marengo, 2010). Climate change has, in fact, led to significant concerns regarding conservation efforts for many marine mammals worldwide, as certain specific characteristics, such as specialized diets, restricted ranges, or reliance on specific substrates   (2): 5-7. 2021 or sites make many marine mammal populations particularly vulnerable to climate change (Silber et al., 2017). Manatees could, thus, have benefited from this condition and gathered in the region, resulting in this mating aggregation. In such a case, female in estrus can attract reproductive males or subadults looking for a chance to reproduce (Hartman, 1979). In practice, the opportunity to witness such an elusive event in turbid waters is rather unlikely, and suggests that Amazonian manatees are probably reoccupying Belém area and its vicinities, as well as the eastern coast of Pará state, at unprecedent rates for a large aquatic mammal. It is also important to note that the world has experienced the COVID-19 pandemic in the last two years, where the use of public areas has changed, and in some stages of the pandemic, people and vessels were not allowed in the Mosqueiro area. Although isolation rules have been reduced in the end of 2021, the use of these places has not returned to normal. No previous studies or during the SARS-CoV-2 pandemic are available to confirm that manatees may have increased their use of the region due to a reduced human presence. This event, never-before-seen and filmed near Belém, should be highlighted and may serve as baseline for future studies, to identify whether the Amazonian manatees come closer or move away from the beach area with the normal use by humans.
Continued field studies on the manatee population in this area are still lacking, especially with regard to population size, area use and behavior. This report can, thus, contribute to this goal, with the potential to be used as basis for more complex studies, including those employing information from the local community, which is especially noteworthy in view of the importance of the role Local Ecological Knowledge (LEK) -comprising knowledge, uses and practices regarding ecological relationships gained through extensive personal observation of and interaction with local ecosystems, and shared among local resource users -plays in conservation strategies (Camino et al., 2020).
Finally, this remarkable observation concerning the reproductive behavior in Amazonian manatees brings hope for their long-term recovery. Community records and the Bicho D'água NGO efforts over the years indicate Mosqueiro as a valuable area for Amazonian manatees, while also demonstrating the need for public policies aimed at the conservation of these endangered and charismatic animals in the region.

ACKNOWLEDGMENTS
Greicy F. Ruenes kindly prepared the map. S. Siciliano is supported by INOVA/Fiocruz and CNPq (Produtividade em Pesquisa). We are grateful to the residents and staff of the local Fire Department, who provided us with information, as well as pictures of the manatees.