Biology subjects

Gero, S.

Publications and source records attributed to Gero, S..

5 recordsLinked to original sources

bioRxiv2026

Sperm whale foraging combines persistent search with flexible prey-capture tactics

Predators searching patchy environments must coordinate movements across scales, yet this behavioural hierarchy is not yet technically possible to observe in the deep ocean. Here we show that sperm-whale foraging is organized across two nested levels: directionally persistent search paths and flexible prey-capture tactics. We combine acoustic recordings with reconstructed three-dimensional trajectories from 34 sensor-tag deployments on 20 individual whales in both the eastern Caribbean and the mid-Atlantic. Complete foraging paths exhibit heavy-tailed step lengths and superdiffusive displacement, consistent with Levy-like search. Within these paths, echolocation buzzes resolve into two recurrent acoustic-kinematic tactics. Type A involves brief ramp-ups, slower and more oscillatory movement, and longer post-buzz pauses. Type B involves prolonged ramp-ups, faster and vertically persistent movement, greater roll, slightly straighter approaches, and an energy-model estimate approximately seven times higher. Every sampled whale used both tactics and switched between them within dives, showing that the contrast is not driven by specialization among individuals. An Azorean deployment with prey-field echograms links the tactics to local prey conditions, while independent Dominica deployments recover their core kinematic contrast. Together, these results reveal a foraging hierarchy in which flexible capture actions unfold within persistent, deliberate large-scale search.

animal behavior and cognition↗

bioRxiv2025

The phonology of sperm whale coda vowels

In previous research, sperm whale codas (structured series of clicks used for communication) have been shown to resemble human vowels acoustically. Based on the number of formants, two different coda quality categories have been described: a-codas and i-codas. In the present paper, we demonstrate that sperm whale codas not only resemble human vowels acoustically, but also pattern like them across several dimensions. First, traditional count- and timing-based coda types interact with coda "vowel" quality (a vs. i). Second, a-codas are generally longer than i-codas. Third, the duration of i-codas has a bimodal distribution, showing a contrast between short i-codas and long[i] -codas. Fourth, the baseline coda length differs across whales. And fifth, edge clicks mismatching their coda often match an adjacent coda, a phenomenon that resembles human coarticulation. All five properties have close parallels in the phonetics and phonology of human languages. Sperm whale coda vocalizations thus represent one of the closest parallels to human phonology of any known animal communication system. SIGNIFICANCE STATEMENTSperm whales communicate using series of clicks known as codas. The codas acoustically resemble human vowels. In addition, they pattern in ways similar to human sound systems. For example, different coda types are correlated with particular click qualities, and their durations are intentionally controlled. This shows that sperm whale vocalizations are highly complex and likely constitute one of the most sophisticated communication systems in the animal kingdom. By studying it, we may be able to gain a broader understanding of animal intelligence and social behaviors, determine the impact of human activities on whale habitat, develop strategies to protect whales from threats such as noise pollution and ship traffic, and advance legislation which facilitates that protection.

animal behavior and cognition↗

bioRxiv2024

WhaleLM: Finding Structure and Information in Sperm Whale Vocalizations and Behavior with Machine Learning

Language models (LMs), which are neural sequence predictors trained to model distributions over natural language texts, have come to play a central role in human language technologies like machine translation and information retrieval. They have also contributed to the scientific study of human language itself, enabling progress on long-standing questions about the learnability, optimality, and universality of key features of human languages. Many analogous questions exist in the study of communication between non-human animals--for which, in many cases, we have only a preliminary understanding of signals structure and use. Can neural sequence models help us understand these animal communication systems as well? We use these models to characterize the structure and information content of sperm whale vocalizations. Sperm whales (Physeter macrocephalus) engage in complex, coordinated behaviours like foraging and navigation in the darkness of the ocean while exchanging sequences of rhythmic clicks known as codas. However, little is known about whether there are any systematic patterns governing coda production, or how codas influence group decision-making and behaviour. To begin to answer these questions, we first train a neural sequence model (a sperm whale language model) to predict whales future vocalizations from their conversational history. By systematically manipulating the information available to this model, and measuring the change in predictive accuracy, we show that sperm whale vocalizations exhibit order dependence, long-range dependencies on up to the past eight codas in an exchange, and predictable turn-taking. Second, we train the sequence model to predict whales behaviour from their vocal exchanges, and find that both current behavioural context and future actions are predictable, with accuracies of 72% and 86% respectively, from coda sequences. Our study provides the first evidence that sperm whale vocalizations contain information that could be used to coordinate behaviour. More generally, it offers a framework for using modern machine learning tools for hypothesis generation and to assist in investigating the structure and function of unknown communication systems.

animal behavior and cognition↗

bioRxiv2023

Contextual and Combinatorial Structure in Sperm Whale Vocalisations

Sperm whales (Physeter macrocephalus) are long-lived and highly social mammals that engage in complex group behaviours, including navigation, foraging, and child-rearing. During these behaviours, sperm whales communicate primarily using sequences of short bursts of clicks with varying inter-click intervals, known as codas. Past research has identified around 150 discrete coda types globally, with 21 in the Caribbean. A subset of these have been shown to encode information about caller and clan identity. However, almost everything else about the sperm whale communication system, including basic questions about its structure and information-carrying capacity, remains unknown. In this study, we show that codas exhibit contextual and combinatorial structure with key similarities to aspects of human language and other primate communication systems. First, we report previously undescribed variations in coda structure that are sensitive to the conversational context in which they occur. We call these rubato and ornamentation, by analogy to musical terminology. These variations are systematically controlled and imitated across individual whales. Second, we show that coda types are not defined by arbitrary sequences of inter-click intervals, but instead form a combinatorial coding system in which rubato and ornamentation combine with two categorical, context-independent features that we call rhythm and tempo to give rise to a large inventory of distinguishable codas. In a dataset of 8,719 codas from the sperm whales of the Eastern Caribbean clan, this sperm whale phonetic alphabet makes it possible to systematically explain observed variability in coda structure. Sperm whale vocalisations are more expressive and structured than previously believed, and are built from a repertoire comprising nearly an order of magnitude more distinguishable codas. These results show contextsensitive and combinatorial vocalisation systems extend beyond humans, and can appear in an organism with a divergent evolutionary lineage and vocal apparatus.

animal behavior and cognition↗

bioRxiv2021

Comparison of Three Individual Identification Algorithms for Sperm Whales (Physeter macrocephalus) after Automated Detection

Photo-identification of individual sperm whales (Physeter macrocephalus) is the primary technique for mark-recapture-based population analyses for the species The visual appearance of the fluke -- with its distinct nicks and notches -- often serves as the primary visual differentiator, allowing humans to make recorded sightings of specific individuals. However, the advent of digital photography and the significant increase in volume of images from multiple projects in combination with pre-existing historical catalogs has made applying the method more challenging.with the required human labor for de-duplication (reduction of Type II errors) and reconciliation of sightings between large datasets too cost- and time-prohibitive. To address this, we trained and evaluated the accuracy of PIE v2 (a triplet loss network) along with two existing fluke trailing edge-matching algorithms, CurvRank v2 and Dynamic Time Warping (DTW), as a mean to speed comparison among a high volume of photographs. Analyzed data were collected from a curated catalog of well-known sperm whales sighted across years (2005-2018) off the island of Dominica. The newly-trained PIE model outperformed the older CurvRank and DTW algorithms, and PIE provided the following top-k individual ID matching accuracy on a standard min-3/max-10 sighting training data set: Rank-1: 87.0%, Rank-5: 90.5%, and Rank-12: 92.5%. An essential aspect of PIE is that it can learn new individuals without network retraining, which can be immediately applied in the presence of (and for the resolution of) duplicate individuals in overlapping catalogs. Overall, our results recommend the use of PIE v2 and CurvRank v2 for ID reconciliation in combination due to their complementary performance.

ecology↗