Abstract

MORALES LOPEZ, Margarita; OLIVERA-GOMEZ, León David  and  ZENTENO-RUIZ, Claudia Elena. Breath rate and displacement in Antillean manatees Trichechus manatus manatus (MAMMALIA: SIRENIA), comparison among dry and rainy seasons in an isolated lake. Mastozool. neotrop. [online]. 2012, vol.19, n.1, pp.117-126. ISSN 0327-9383.

Dry season reduces water level in fluvial-lake systems associated to large rivers at southern Gulf of Mexico, limiting the available food for Antillean manatees (Trichechus manatus manatus) that remain on these systems. To determine if manatee´s activity changes among dry (reduced food availability) and rainy season, we registered the extension of movements and breath interval from radio-tagged manatees (VHF system) on each season at "Laguna de las Ilusiones," Tabasco, Mexico, on sessions 40 min long, alternating between morning and afternoon. The study was conducted in 2009, from May to July (dry season) and from September to November (rainy season). Observations were registered at ca. 200 m from the animal. Mean value of movements at the dry season was 739.3 ± 163.8 m (n = 5) and 928.4 ± 252.2m (n = 23) for rains. On dry season, the breath interval was 144.39 ± 19.57 sec (n = 5) and 40.37 ± 9.114 sec (n = 25) for rains. Variability was estimated by 1000 bootstrap subsamples. Five-hundred subsamples of five elements from the rains were contrasted with dry samples through a Two-Sample Fligner-Policello Robust Rank Order Test. There were significant differences (P < 0.05) in 64 and 433 of the 500 simulations for movements and breath interval. Data support the idea that manatees are less active at the dry season. Energetic stress at dry season could be minimized by lowering their activity, however, this renders manatee prone to collisions by boats and other threats.

Keywords : Activity; Antillean manatee; Breath interval; Dry season; Limited food; Movements; Radio tagging.