Tagging young humpback whale calves: methodology and diving behavior

Abstract

Despite the importance of young animals to the proliferation of a species, logistic hurdles often prevent the study of individuals' behavior and habitat requirements. This is particularly an issue in the case of cetaceans, which spend a large proportion of their time at depth. We conducted a study to describe the dive behavior of young humpback whale Megaptera novaeangliae calves on their breeding grounds in Hawaii, USA. We first implemented and evaluated strategies for approaching whale groups and deploying suction-cup tags (DTAGs), resulting in 3 successful attachments of DTAGs in the winter of 2011. The approach technique that was most successful while minimizing reactions from the whale groups was a passive drift approach. Tagged calves exhibited consistent dives to shallow depths when their groups were stationary, and some deeper dives that approached the ocean bottom, up to 78 m in one case. Mean dive durations ranged from 2.2 to 3.5 min, with calves spending 40% of their time within 3 m of the surface. This is the first study to collect tag data from baleen whale calves less than 6 mo in age and provides habitat use data important for management of this endangered species. KEY WORDS: Humpback whale · Calf · Tagging · Diving behavior · Hawaii Resale or republication not permitted without written consent of the publisherEndang Species Res 19: 11-17, 2012 proven to be low-impact, scientists and managers refrained from deploying them on young calves. Tagging of adults with suction-cup tags has been reported to elicit mild and short-term reactions in most large species (Hooker et al. 2001, Johnson et al. 2009), although some smaller species have reacted more strongly and for a longer duration (Schneider et al. 1998). Biopsy sampling of large whales, which also involves close boat approaches, has also resulted in only mild behavioral reactions (Weinrich et al. 1992, Clapham & Mattila 1993, Brown et al. 1994. Given this precedent, we believed that, if conducted mindfully and conservatively, tagging of calves has the potential to yield valuable information on young animal behavior with minimal distress to the ap proached and tagged individuals.Our goals with this manuscript are 2-fold. First we document our field procedures for tagging humpback whale calves on their breeding grounds, comparing 2 approach tactics and making recommendations on strategy for future experiments tagging young baleen whale calves. We then present a basic description of the diving behavior of the tagged animals, the first such description for this life stage of a baleen whale. MATERIALS AND METHODS Study locationThis research was conducted between February 21 and March 4, 2011 in the leeward waters of Maui, Hawaii, USA. The research vessels included the RV 'Hihimanu' (hereafter 'big boat') and a 17 ft inflatable. The big boat was an 11 m safe boat style vessel with twin 250 hp Mercury 4-stroke outboard engines. The inflatable had a 25 hp Mercury 2-stroke outboard engine and could also be propelled by 2 people paddling with...

High suckling rates and acoustic crypsis of humpback whale neonates maximise potential for mother–calf energy transfer

“…The vertical speed during ascent and descent in suckling dives (grand mean vertical speed of 0·6 ± 0·1 m s −1 ) is in accordance with previous dive data of young humpback whale calves on breeding grounds (Stimpert et al . ). Suckling dives had a grand mean duration of 2·1 ± 0·9 min of which 47–88% (Table ) of the total dive duration was spent in suckling position on average.…”

The effect of close approaches for tagging activities by small research vessels on the behavior of humpback whales (Megaptera novaeangliae)

“…, Stimpert et al . ). Therefore, behavioral observation studies that use close vessel approaches may need to take group composition into account when collecting data on potentially sensitive cohorts, such as humpback whale female‐calf groups.…”

“…, Stimpert et al . ). Group composition has also been found to be an important factor when looking at behavioral responses.…”

“…, Stimpert et al . ). Therefore, when analyzing behavioral responses in cetaceans, to prevent masking of significant effects, it may be useful to examine any potential variability between cohorts.…”

“…For example Stimpert et al . () found that slow approaches caused minimal apparent impact on group behavior when tagging Antarctic humpback whales compared to faster methods.…”