<p>In 2010, the Instituto Araguaia, a local NGO, started a program to protect and monitor giant otters, and to use them as an umbrella and flagship species for the conservation of the Cantão ecosystem. As part of the program, a census was carried out to determine the giant otter population of a group of 16 lakes in the park, and this population was monitored over a 28-month period spanning three breeding seasons, between September 2010 and December 2012.</p>
RESUMOO cerrado rupestre possui grande riqueza de espécies endêmicas e raras, mesmo assim apresenta uma área cada vez mais reduzida, principalmente devido à ação antrópica. O presente trabalho realizou o levantamento da estrutura arbustivoarbórea em uma área remanescente de cerrado rupestre, onde a visitação humana é intensa devido ao ecoturismo. Foram utilizadas 10 parcelas permanentes de 20 x 50 m (1 ha), sendo amostrados todos os indivíduos com diâmetro igual ou superior a 5,0 cm a 30 cm do solo. Foram calculados os valores absolutos e relativos de densidade, dominância, frequência, valor de importância e área basal, o índice de diversidade de Shannon (H') e o de uniformidade de Pielou (J). A densidade total da área foi de 543 indivíduos.ha -1 distribuídos em 58 espécies, 46 gêneros e 28 famílias. A área basal foi de 4,6 m². As famílias com maior número de espécies foram: Fabaceae (8) e Vochysiaceae (7). Quinze famílias foram representadas por uma única espécie e 16 espécies apresentaram apenas um indivíduo. Qualea parviflora, Davilla elliptica, Sclerolobium paniculatum var. subvelutinum, Miconia ferruginata, Caryocar brasiliense apresentaram os maiores índices de valor de importância. Foi registrada pela primeira vez no cerrado rupestre do estado de Goiás a espécie Hirtella gracilipes, típica da formação de Cerradão. O índice de Shannon (H') foi de 1,51 e o de uniformidade de Pielou (J) igual a 0,37, valores baixos quando comparados com outras áreas de cerrado rupestre, indicando que esta área pode estar sofrendo ações de degradação provocada principalmente pela intensa visitação humana. PALAVRAS-CHAVE: Afloramentos rochosos, flora lenhosa. Fitossociologia.
We carried out monthly surveys of the giant otter population between 2010 and 2020 in a study area comprised of 1,500 hectares of igapo flooded forest with oxbow lakes in the Cantao region of central Brazil. We recorded 16-32 resident adults in the study area each year, distributed in 4-8 groups. Resident groups exhibited extensive home range overlap, with each group using several lakes and larger lakes used in rotation by up to six groups. Dens and campsites were also shared by multiple groups, but lakes were used by only one group at a time, and encounters between groups were very rare. 24 adult otters were observed to join an existing group. Some individuals changed groups multiple times. Resident adult turnover was high. Each year an average of 36% of resident adults were new immigrants, and 72% of groups left the area within two years. Resident groups had, on average, one litter every three years, and annual cub production showed high variability and a negative correlation to the number of new immigrants in the area. No pairs of giant otters reproduced successfully during the study. Groups of three otters formed through the recruitment of an adult individual by an existing pair and reproduced as successfully as larger groups. Group dynamics and territorial behavior in the Cantao flooded forest ecosystem, where optimal giant otter habitat is continuous in all directions, were found to be different from that reported in areas composed of patchy (isolated oxbow lakes) or linear (rivers) habitat. This suggest that giant otter social and territorial behavior is plastic and adapts to the spatial characteristics of the habitat.
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