Decreases in encounter rate of endangered Northeast Pacific humpback whales in Southern Costa Rica: Possible changes in migration pattern due to warming events

Abstract

Warming events in the Pacific Ocean are becoming more frequent, intense, and on a larger temporal and spatial scale. This has caused critical habitats of marine species to lose their quality and marine organisms respond by modifying their critical feeding and reproduction behaviors, as well as their distribution. The Northeast Pacific humpback whale of the Central America distinct population segment (DPS) remains Endangered due to its small population size and because its response to climate change and human interventions is unknown. In this work, we showed the encounter rates of humpback whales in their breeding grounds in Costa Rica for breeding seasons comprised in the period 2000-2020. We analyze the influence of climatic indices that influence the Pacific and environmental variables related to temperature and productivity in the feeding grounds of this population (United States). We hypothesize that the more intense the warming events, the fewer humpback whales complete their migration to Costa Rica. We conclude that the humpback whales of this population could be finding thermally favorable areas in intermediate latitudes (p. e.g., Mexican-Guatemala coasts), which could be related to the decreases in the presence of humpback whale adults and calves in Costa Rica. These observed changes could inform how humpback whales might respond to climate change.

The migratory whale herd concept: A novel unit to conserve under the ecological paradigm

“…Population structure that is mediated by behavior learned during the natal migration might be expected to change more rapidly than population structure defined by geographical constraints, possibly conferring greater resiliency to the changes in habitat quality expected to result from climate change (Keith & Bull, 2017). For humpback whales, there are numerous studies documenting shifts in feeding ground distribution and migratory timing in response to environmental variation (Askin et al, 2017; Avila et al, 2020; Pelayo‐González et al, 2022; Schall et al, 2021a,b; Szesciorka et al, 2022). However, the lack of recovery of some herds following cessation of industrial whaling suggests that strong intergenerational fidelity to wintering and feeding grounds may inhibit some migratory whale species’ ability to adapt to a changing environment (Brakes et al, 2021; Carroll et al, 2015).…”

“…As a result, their genetic, demographic, and population structure are likely out of equilibrium, and are unlikely to reach equilibrium any time soon. Numerous studies have documented distributional shifts on humpback feeding grounds and changes in migration timing in response to changing environmental conditions (Askin et al, 2017; Avila et al, 2020; Pelayo‐González et al, 2022; Schall et al, 2021a,b; Szesciorka et al, 2022). Extreme environmental conditions may also play a role in some movements of animals between wintering grounds (Félix et al, 2020; Stevick et al, 2013).…”

Genetic data reveal wintering ground affiliation of humpback whales from the Mexican Central Pacific

“…The change in haplotype frequencies we observed in 2016 coincided with a strong El Niño, as well as a marine heatwave event in the North Pacific (Di Lorenzo & Mantua, 2016; Holbrook et al, 2019). These climate anomalies resulted in shifts in the distribution of humpbacks on both feeding and wintering grounds around the world (Askin et al, 2017; Félix et al, 2020; Gabriele et al, 2022; Schall et al, 2021), including for the MX and CEA whales (Ortega‐Ortiz et al, 2022; Pelayo‐González et al, 2022). Sighting rates dropped precipitously in the 2016 season compared to other years in both Costa Rica, which is part of the CEA wintering area (Pelayo‐González et al, 2022), and in COL (Ortega‐Ortiz et al, 2022).…”

“…These climate anomalies resulted in shifts in the distribution of humpbacks on both feeding and wintering grounds around the world (Askin et al, 2017; Félix et al, 2020; Gabriele et al, 2022; Schall et al, 2021), including for the MX and CEA whales (Ortega‐Ortiz et al, 2022; Pelayo‐González et al, 2022). Sighting rates dropped precipitously in the 2016 season compared to other years in both Costa Rica, which is part of the CEA wintering area (Pelayo‐González et al, 2022), and in COL (Ortega‐Ortiz et al, 2022). In both cases, the authors hypothesized that whales migrate further south in colder years, and end their migrations further north in warm years, like 2016.…”