The role of touch in captive and semi-captive Antillean manatees (Trichechus manatus manatus)

Abstract

Tactile signals have been neglected in aquatic animal studies despite being a major communication modality. We investigated Antillean manatees’ tactile behavioural repertoire and budget in captivity (7-females and 4-males) and semi-captivity (4-males) in Brazil. We detected 17 tactile behaviours (14.03% of the activity budget) with social, self-maintenance, or environmental exploration functions. The observation method influenced the detection of self-maintenance behaviours — focal animal and ad libitum detected more of these behaviours than scan sampling. Age, sex, housing, and centre routines influenced the tactile repertoire. The captive females and semi-captive males tactile patterns differed, suggesting that sex and animal-pool density play a role in tactile patterns. We recommend carefully choosing the observation method when investigating functional categories of manatee tactile behaviours. The monitoring and stimulation of manatee tactile behaviours should integrate rehabilitation and reintroduction practices. Environmental enrichment may stimulate tactile behaviours related to habitat exploration, key behaviours in aiding manatee navigation.

Visual and acoustic exploratory behaviors toward novel stimuli in Antillean manatees (Trichechus manatus manatus) under human care.

“…Since manatees have extra sensitivity in tactile sensory systems, the objects introduced in their pool might be better detected because of the movement of the water they generate, which may explain why manatees displayed more reactions for the floating and submerged objects. Similarly to our study, Antillean manatees have been observed frequently interacting with coconuts floating above the water in rehabilitation pools (Lucchini et al, 2021). In our study, individuals were habituated to the presence of grass, other species, and humans around their pool, and were exposed to various types of sounds linked to anthropogenic activities or other species in their environment.…”

“…Also, manatees frequently interacted with keepers diving in their pool and might have learned to pay attention to submerged items. Some studies emphasized that the vibrissae present over the entire body are a major source of sensation (Bauer & Reep, 2018; Lucchini et al, 2021). Indeed, manatees are able to discriminate precisely between different object textures and also detect small water movements (Bauer et al, 2012).…”

“…Indeed, manatees are able to discriminate precisely between different object textures and also detect small water movements (Bauer et al, 2012). The role of touch in captive Antillean manatees’ behavior has been also mentioned, and environmental exploration represented around 70% of the overall tactile behaviors (Lucchini et al, 2021). Also, manatees’ in-air acuity has not been studied properly and could be much more limited than their underwater vision, thus increasing the difficulty to detect out-of-water objects.…”

“…Manatees are described as discreet, docile animals (i.e., not very aggressive toward humans) but can sometimes be curious and exploratory (Hartman, 1979). These animals have been frequently observed interacting with their environment, for example, catching and manipulating objects with their flippers and upper lip (Hartman, 1979;Horikoshi-Beckett & Schulte, 2006;Lucchini et al, 2021). In some cases, manatees have been observed achieving contact with divers or exploring certain types of boats (Hartman, 1979;Marsh, 2022).…”