Good vibrations by the beach boys: magnitude of substrate vibrations is a reliable indicator of male grey seal size

Communication via Biotremors in the Veiled Chameleon (Chamaeleo calyptratus): Part I- Biotremor Production and Response to Substrate-Borne Vibrations

Biotremors are vibrations, usually surface waves along the boundary of a medium, produced by an organism. While substrate-borne vibrations are utilized by different reptile species, true conspecific communication via biotremors has not yet been demonstrated in lizards. Recent research revealed that the veiled chameleon (Chamaeleo calyptratus) produces biotremors. The prerequisites for any communication system are the ability of an organism to produce and detect a signal. We tested C. calyptratus behavioral responses to vibrations by placing them on a dowel attached to a shaker, emitting vibrations of 25, 50, 150, 300, and 600 Hz and compared their locomotory velocity before and after the stimulus. Adult chameleons exhibited a freeze response to 50 and 150 Hz, while juveniles exhibited a similar response to frequencies between 50 and 300 Hz. In a second experiment, chameleons were induced to produce biotremors via experimenter contact. These biotremors ranged in mean fundamental frequency from 106.4 to 170.3 Hz and in duration from 0.06 to 0.29 s. Overall, two classes of biotremors were identified, "hoots" and "mini-hoots," which differed significantly in mean relative signal intensity (-7.5 and -32.5 dB, respectively). Juvenile chameleons 2 months of age were able to produce biotremors, suggesting this behavior may serve a wide range of ecological functions throughout ontogeny. Overall, the data demonstrate that C. calyptratus can both produce and detect biotremors that could be used for intraspecific communication.

Biotremology in arthropods

Effective communication is essential in animal life to allow fundamental behavioral processes and survival. Communicating by surface-borne vibrations is likely the most ancient mode of getting and exchanging information in both invertebrates and vertebrates. In this review, we concentrate on the use of vibrational communication in arthropods as a form of intraspecific and interspecific signaling, with a focus on the newest discoveries from our research group in terrestrial isopods (Crustacea: Isopoda: Oniscidea), a taxon never investigated before in this context. After getting little attention in the past, biotremology is now an emerging field of study in animal communication, and it is receiving increased interest from the scientific community dealing with these behavioral processes. In what follows, we illustrate the general principles and mechanisms on which biotremology is based, using definitions, examples, and insights from the literature in arthropods. Vibrational communication in arthropods has mainly been studied in insects and arachnids. For these taxa, much evidence of its use as a source of information from the surrounding environment exists, as well as its involvement in many behavioral roles, such as courtship and mating, conspecific recognition, competition, foraging, parental care, and danger perception. Recently, and for the first time, communication through surface-borne waves has been studied in terrestrial isopods, using a common Mediterranean species of the Armadillidae family as a pilot species, Armadillo officinalis Duméril, 1816. Mainly, for this species, we describe typical behavioral processes, such as turn alternation, aggregation, and stridulation, where vibrational communication appears to be involved.

Get off my back: vibrational assessment of homeowner strength

Animals may use a variety of sensory modalities to assess ownership and resource-holding potential (RHP). However, few studies have experimentally tested whether animals can assess these key variables through a purely vibrational modality, exclusively involving substrate-borne vibrations. Here we studied social terrestrial hermit crabs ( Coenobita compressus), where competitors assess homeowners by climbing on top of a solid external structure-an architecturally remodelled shell home, inside of which the owner then produces vibrations. In the field, we used a miniature vibratory device, hidden within an empty shell, to experimentally simulate a 'phantom owner', with variable amplitudes of vibration representing different levels of homeowner strength. We found that assessors could use these vibrations to deduce the owner's RHP: for strong vibrations (indicative of a high RHP owner) assessors were least likely to escalate the conflict; for weak vibrations (indicative of a low RHP owner) assessors showed intermediate escalation; and in the absence of vibration (indicative of an extremely weak or absent owner) assessors were most likely to escalate. These results reveal that animals can assess homeowner strength based solely on substrate vibrations, thereby making important decisions about whether to escalate social conflicts over property.

Shipping noise in a dynamic sea: a case study of grey seals in the Celtic Sea

Shipping noise is a threat to marine wildlife. Grey seals are benthic foragers, and thus experience acoustic noise throughout the water column, which makes them a good model species for a case study of the potential impacts of shipping noise. We used ship track data from the Celtic Sea, seal track data and a coupled ocean-acoustic modelling system to assess the noise exposure of grey seals along their tracks. It was found that the animals experience step changes in sound levels up to ~20dB at a frequency of 125Hz, and ~10dB on average over 10-1000Hz when they dive through the thermocline, particularly during summer. Our results showed large seasonal differences in the noise level experienced by the seals. These results reveal the actual noise exposure by the animals and could help in marine spatial planning.