Interchange of Southern Hemisphere humpback whales across the South Atlantic Ocean

Abstract

The cosmopolitan distribution of humpback whales (Megaptera novaeangliae) is largely driven by migrations between winter low-latitude breeding grounds and summer high-latitude feeding grounds. Southern Hemisphere humpback whales faced intensive exploitation during the whaling eras and recently show evidence of population recovery. Gene flow and shared song indicate overlap between the western (A) and eastern (B1, B2) Breeding Stocks in the South Atlantic and Indian Oceans (C1). Here, we investigated photo-identification evidence of population interchange using images of individuals photographed during boat-based tourism and research in Brazil and South Africa from 1989 to 2022. Fluke images were uploaded to Happywhale, a global digital database for marine mammal identification. Six whales were recaptured between countries from 2002 to 2021 with resighting intervals ranging from 0.76 to 12.92 years. Four whales originally photographed off Abrolhos Bank, Brazil were photographed off the Western Cape, South Africa (feeding grounds for B2). Two whales originally photographed off the Western Cape were photographed off Brazil, one traveling to the Eastern Cape in the Southwestern Indian Ocean (a migration corridor for C1) before migrating westward to Brazil. These findings photographically confirm interchange of humpback whales across the South Atlantic and Indian Oceans and the importance of international collaboration to understand population boundaries.

Abrupt change in humpback whale song from Brazil suggests cultural revolutions may occur in the South Atlantic

“…However, Darling and Sousa-Lima (2005) showed strong similarity between songs from BSA and BSB, suggesting that "wandering males" could circulate between both areas allowing such acoustic contact. In fact, recent evidence of a whale initially registered in the Eastern Cape in South Africa in November 2017 was resighted off Brazil in August 2018 (represented by a purple triangle in Figure 1; Ramos et al, 2023). This coincides with the year in which the abrupt song change was observed.…”

“…The orange triangle represents a resighting of another humpback whale first seen in Brazil and then in Madagascar (Stevick et al, 2011), and the green triangle indicates resightings of six different humpback whales seen off the Brazilian coast and in the Western Antarctic Peninsula (Marcondes et al, 2021). The purple triangles represent re-sightings of 6 individuals of humpback whales observed between the Brazilian coast and South Africa (Ramos et al, 2023). The stars represent the areas where data were collected in Brazil, the Abrolhos Bank and Serra Grande (both off Bahia state).…”

“…Moreover, an individual belonging to BSG and photo-identified in Ecuador in 2006 and 2008, was registered in the Abrolhos Bank in 2016 (represented with a blue triangle in Figure 1; Felix et al, 2020). Other five individuals were photographed between Brazil and South Africa from 2002 to 2021 (Ramos et al, 2023). These movements do not provide evidence that individual humpback whales can undertake these alternative and longer migrations during a single breeding season, but Darling et al (2022) recently showed that whales do visit two different wintering grounds within the same breeding season in the Northern Hemisphere, providing the precedent of such long distance traveling in humpback whales.…”

Cetacean diversity of the eastern South Atlantic Ocean and Vema Seamount detected during a visual and passive acoustic survey, 2019

“…There is some genetic differentiation between humpback whales from western South Africa and Gabon, but with some known interchange of biopsied and photographically identified individuals between these sub-stocks (Rosenbaum et al, 2009;Barendse et al, 2011). It is therefore possible that these whales use different migration routes to the feeding grounds, and that song is exchanged while on the high-latitude feeding grounds (Best and Allison, 2010;Barendse et al, 2011;Schall et al 2022, Ramos et al, 2023.…”

Evaluating wildlife tourism exposure to Florida manatees using citizen science, public interviews, and trail cameras

“…Trail cameras, also known as motion‐triggered cameras, have been frequently used for detecting human activity in the marine environment such as monitoring the presence of boats, track time spent in the water (Stahr & Knudsen, 2018) and investigate unregulated fishing in protected areas (Ban et al, 2020). Citizen science engages the public in scientific data collection (Dickinson et al, 2010) and has been used widely in a variety of tourism‐based projects which include photo‐identification for whales (Cheeseman et al, 2017; Ramos et al, 2023) and monitoring dolphin presence (Currie et al, 2018). For instance, in Kenya, researchers documented the presence of small cetaceans by providing training to tour operators and fishermen (Mwango'mbe et al, 2021).…”