Social Behaviour of Humpback Whales (Megaptera novaeangliae) in Hervey Bay, Eastern Australia, a Preferential Female Stopover During the Southern Migration

Trish Franklin,Peter Harrison,Wally Franklin,Adam A Pack,Lyndon Brooks,Phillip J Clapham

doi:10.3389/fmars.2021.652147

Abstract

Agonistic competitive social behaviour in humpback whales [Megaptera novaeangliae(Borowski, 1781)] has been extensively studied and reported in previous research. However, non-agonistic social behaviour in humpback whale pods has not been systematically studied. We investigated the social behaviour of 3,949 humpback whale pods over a period of 14 years during August, September, and October in Hervey Bay (Queensland, eastern Australia), a preferential female stopover early in the southern migration. Modelling and analyses of the data examined the factors influencing the occurrence and timing of non-agonistic social behaviour pods, agonistic competitive pods and newly associated pods. Non-agonistic social behaviour was observed more frequently during August when mature females, including early pregnant and resting females, co-occur and socially interact with immature males and females. Overall, relatively few mature males visit Hervey Bay. Agonistic competitive behaviour was observed with increasing frequency during September and October when mother-calf pods, with few escorts predominated. Mother-calf pods in Hervey Bay spent most of their time alone involved in maternal care. Agonistic competitive behaviour is related to the decreasing numbers of potentially oestrous females toward the end of the season. Non-agonistic social behaviour and agonistic competitive behaviour were more frequently observed in larger and newly associated pods. Overall, non-agonistic social behaviour pods were more prevalent than agonistic competitive social behaviour pods. The results of this study substantiate that non-agonistic social behaviour may be more prevalent than aggressive agonistic social behaviour in site-specific locations and habitats, depending upon the classes and timings of humpback whales using such habitats.

Highlights

Humpback whales (Megaptera novaeangliae) are a migratory species
Our results provide the first systematic seasonal study of non-agonistic social behaviour and agonistic competitive social behaviour in humpback whale pods in a site-specific femalebiassed stopover along the southern migratory route from the eastern Australian breeding grounds
There are important differences and similarities with humpback whale behaviour in Hervey Bay compared with behaviour reported in Northern Hemisphere breeding grounds and feeding areas, and along some migratory corridors in the Southern Hemisphere

Summary

Introduction

Humpback whales (Megaptera novaeangliae) are a migratory species. Except for humpback whales in the Arabian Sea (Mikhalev, 1997), individual females and males, in all maturational classes, and different reproductive states, in all other populations, migrate from high-latitude summer/autumn feeding areas to low latitude winter/spring breeding grounds (Chittleborough, 1965; Dawbin, 1966; Clapham and Mead, 1999). Feeding is rare or absent in winter breeding grounds, when most behaviours are related to calving and mating The latter includes singing of long, complex song by male humpbacks to either attract females and/or meditate intrasexual interactions with other males (Payne and McVay, 1971; Clapham, 1996; Darling et al, 2006; Herman, 2017). Humpback whale social behaviour and demographics in the feeding areas and breeding grounds in the Northern Hemisphere, as well as along some migratory routes, have been well described (see summaries in Clapham, 1993, 2000; Herman, 2017). There is relatively little understanding about the behaviours and demographics of humpback whales in so-called “stopover” habitats along migratory routes, to and from feeding areas and breeding grounds. The use of so-called “stopovers” for rest, refuelling and predator avoidance, is not uncommon in species that undergo relatively long migrations including insects (Kennedy, 1951; McCord and Davis, 2012), reptiles (Rice and Balazs, 2008; Baudouin et al, 2015; Dujon et al, 2017; Nivière et al, 2018), mammals (e.g., Sawyer and Kauffman, 2011), and numerous bird species (e.g., Alerstam and Hedenström, 1998; Weber et al, 1998; Schaub et al, 2001, 2008; Delmore et al, 2012; McCabe and Olsen, 2015; Zaynagutdinova et al, 2019)

Methods

Results

Conclusion