Whale-call response to masking boat noise

Abstract

Background noise can interfere with the detection and discrimination of crucial signals among members of a species. Here we investigate the vocal behaviour in the presence and absence of whale-watcher boat traffic of three social groups (pods) of killer whales (Orcinus orca) living in the nearshore waters of Washington state. We find longer call durations in the presence of boats for all three pods, but only in recent recordings made following a period of increasing boat traffic. This result indicates that these whales adjust their behaviour to compensate for anthropogenic noise once it reaches a threshold level.

Vibratory noise in anthropogenic habitats and its effect on prey detection in a web-building spider

“…cause signal masking as previously shown in substrate-, air-and waterborne acoustic sensory channels (Bee & Swanson, 2007;Foote, Osborne, & Hoelzel, 2004;McNett et al, 2010;Narins, 1982). We suggest that any increase in sensitivity at high noise treatments would be counteracted by signal masking.…”

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

“…Several delphinid species, including one population of bottlenose dolphins, have been found to increase call duration in relation to boat presence (Foote et al, 2004;Lesage et al, 1999;May-Collado & Wartzok, 2008), while others have not (Buckstaff, 2004;Luís et al, 2014). …”

“…These are summarized by Radford, Kerridge, and Simpson (2014) as (1) avoidance of noise, by moving away from the noise source or adjusting the timing of acoustic signals to coincide with low noise periods, (2) adjustment of acoustic signal temporal parameters, such as increasing call duration or rate, (3) amplitude shifts, such as the 'Lombard effect' whereby animals produce higher amplitude acoustic signals in noise (Lombard, 1911), (4) frequency shifts in acoustic signals or the relative amplitude of signal components and (5) shifting emphasis to an alternative signal modality, for example by increasing the use of visual or chemical signals. Cetaceans are known to respond to boat noise sources in the first four ways (Ansmann, Goold, Evans, Simmonds, & Keith, 2007;Foote, Osborne, & Hoelzel, 2004;Holt, Noren, Veirs, Emmons, & Veirs, 2009;Parks, Clark, & Tyack, 2007;Parks et al, 2011;Rako et al, 2013) and may also increase their use of visual cues in elevated noise conditions (point 5 above, see Dunlop, Cato, & Noad, 2010).…”

The effect of motorboat sound on Australian snapper Pagrus auratus inside and outside a marine reserve

“…For example, killer whales (Foote et al., 2006), humpback whales, (Risch, Corkeron, Ellison, & Van Parijs, 2012), and common dolphins (May‐Collado & Wartzok, 2008) have been shown to shift their call characteristics out of the frequency bands motorboat sound dominates as well as increasing sound levels (Foote, Osborne, & Hoelzel, 2004; Scheifele et al., 2005). Replayed motorboat sound disrupts the orientation behavior of larval reef fish (Holles et al., 2013), which is a critical stage in replenishing fish populations, and fish recruitment and larval survival was effected by motorboat sound, where Ambon damselfish ( Pomacentrus ambionenis ) exposed to motorboat sound had an increase in oxygen consumption and were more susceptible to predators (Simpson et al., 2016).…”