McHugh Katherine

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McHugh
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Katherine
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  • Article
    Field energetics and lung function in wild bottlenose dolphins, Tursiops truncatus, in Sarasota Bay Florida
    (Royal Society, 2018-01-17) Fahlman, Andreas ; Brodsky, Micah ; Wells, Randall S. ; McHugh, Katherine ; Allen, Jason ; Barleycorn, Aaron ; Sweeney, Jay C. ; Fauquier, Deborah A. ; Moore, Michael J.
    We measured respiratory flow rates, and expired O2 in 32 (2–34 years, body mass [Mb] range: 73–291 kg) common bottlenose dolphins (Tursiops truncatus) during voluntary breaths on land or in water (between 2014 and 2017). The data were used to measure the resting O2 consumption rate (V˙O2, range: 0.76–9.45ml O2min−1 kg−1) and tidal volume (VT, range: 2.2–10.4 l) during rest. For adult dolphins, the resting VT, but not V˙O2, correlated with body mass (Mb, range: 141–291 kg) with an allometric mass-exponent of 0.41. These data suggest that the mass-specific VT of larger dolphins decreases considerably more than that of terrestrial mammals (mass-exponent: 1.03). The average resting sV˙O2 was similar to previously published metabolic measurements from the same species. Our data indicate that the resting metabolic rate for a 150 kg dolphin would be 3.9 ml O2 min−1 kg−1, and the metabolic rate for active animals, assuming a multiplier of 3–6, would range from 11.7 to 23.4 ml O2 min−1 kg−1.
  • Article
    Resting metabolic rate and lung function in wild offshore common bottlenose dolphins, Tursiops truncatus, near Bermuda
    (Frontiers Media, 2018-07-17) Fahlman, Andreas ; McHugh, Katherine ; Allen, Jason ; Barleycorn, Aaron ; Allen, Austin ; Sweeney, Jay C. ; Stone, Rae ; Faulkner Trainor, Robyn ; Bedford, Guy ; Moore, Michael J. ; Jensen, Frants H. ; Wells, Randall S.
    Diving mammals have evolved a suite of physiological adaptations to manage respiratory gases during extended breath-hold dives. To test the hypothesis that offshore bottlenose dolphins have evolved physiological adaptations to improve their ability for extended deep dives and as protection for lung barotrauma, we investigated the lung function and respiratory physiology of four wild common bottlenose dolphins (Tursiops truncatus) near the island of Bermuda. We measured blood hematocrit (Hct, %), resting metabolic rate (RMR, l O2 ⋅ min-1), tidal volume (VT, l), respiratory frequency (fR, breaths ⋅ min-1), respiratory flow (l ⋅ min-1), and dynamic lung compliance (CL, l ⋅ cmH2O-1) in air and in water, and compared measurements with published results from coastal, shallow-diving dolphins. We found that offshore dolphins had greater Hct (56 ± 2%) compared to shallow-diving bottlenose dolphins (range: 30–49%), thus resulting in a greater O2 storage capacity and longer aerobic diving duration. Contrary to our hypothesis, the specific CL (sCL, 0.30 ± 0.12 cmH2O-1) was not different between populations. Neither the mass-specific RMR (3.0 ± 1.7 ml O2 ⋅ min-1 ⋅ kg-1) nor VT (23.0 ± 3.7 ml ⋅ kg-1) were different from coastal ecotype bottlenose dolphins, both in the wild and under managed care, suggesting that deep-diving dolphins do not have metabolic or respiratory adaptations that differ from the shallow-diving ecotypes. The lack of respiratory adaptations for deep diving further support the recently developed hypothesis that gas management in cetaceans is not entirely passive but governed by alteration in the ventilation-perfusion matching, which allows for selective gas exchange to protect against diving related problems such as decompression sickness.
  • Article
    Signal-specific amplitude adjustment to noise in common bottlenose dolphins (Tursiops truncatus)
    (Company of Biologists, 2019-11-08) Kragh, Ida M. ; McHugh, Katherine ; Wells, Randall S. ; Sayigh, Laela S. ; Janik, Vincent M. ; Tyack, Peter L. ; Jensen, Frants H.
    Anthropogenic underwater noise has increased over the past century, raising concern about the impact on cetaceans that rely on sound for communication, navigation and locating prey and predators. Many terrestrial animals increase the amplitude of their acoustic signals to partially compensate for the masking effect of noise (the Lombard response), but it has been suggested that cetaceans almost fully compensate with amplitude adjustments for increasing noise levels. Here, we used sound-recording DTAGs on pairs of free-ranging common bottlenose dolphins (Tursiops truncatus) to test (i) whether dolphins increase signal amplitude to compensate for increasing ambient noise and (ii) whether adjustments are identical for different signal types. We present evidence of a Lombard response in the range 0.1–0.3 dB per 1 dB increase in ambient noise, which is similar to that of terrestrial animals, but much lower than the response reported for other cetaceans. We found that signature whistles tended to be louder and with a lower degree of amplitude adjustment to noise compared with non-signature whistles, suggesting that signature whistles may be selected for higher output levels and may have a smaller scope for amplitude adjustment to noise. The consequence of the limited degree of vocal amplitude compensation is a loss of active space during periods of increased noise, with potential consequences for group cohesion, conspecific encounter rates and mate attraction.
  • Article
    Surface and diving metabolic rates, and dynamic aerobic dive limits (dADL) in near‐ and off‐shore bottlenose dolphins, Tursiops spp., indicate that deep diving is energetically cheap
    (Wiley, 2023-04-05) Fahlman, Andreas ; Allen, Austin S. ; Blawas, Ashley ; Sweeney, Jay ; Stone, Rae ; Trainor, Robyn Faulkner ; Jensen, Frants H. ; McHugh, Katherine ; Allen, Jason B. ; Barleycorn, Aaron A. ; Wells, Randall S.
    High‐resolution dive depth and acceleration recordings from nearshore (Sarasota Bay, dive depth < 30 m), and offshore (Bermuda) bottlenose dolphins (Tursiops spp.) were used to estimate the diving metabolic rate (DMR) and the locomotor metabolic rate (LMR, L O2/min) during three phases of diving (descent, bottom, and ascent). For shallow dives (depth ≤ 30 m), we found no differences between the two ecotypes in the LMR during diving, nor during the postdive shallow interval between dives. For intermediate (30 m < depth ≤ 100 m) and deep dives (depth > 100 m), the LMR was significantly higher during ascent than during descent and the bottom phase by 59% and 9%, respectively. In addition, the rate of change in depth during descent and ascent (meters/second) increased with maximal dive depth. The dynamic aerobic dive limit (dADL) was calculated from the estimated DMR and the estimated predive O2 stores. For the Bermuda dolphins, the dADL decreased with dive depth, and was 18.7, 15.4, and 11.1 min for shallow, intermediate, and deep dives, respectively. These results provide a useful approach to understand the complex nature of physiological interactions between aerobic metabolism, energy use, and diving capacity.
  • Dataset
    First evidence for widespread sharing of stereotyped non-signature whistle types by wild dolphins
    (Woods Hole Oceanographic Insitution, 2024-07-30) Sayigh, Laela S. ; Janik, Vincent M. ; Jensen, Frants H. ; McHugh, Katherine ; Tyack, Peter L. ; Wells, Randall S.
    Bottlenose dolphins (Tursiops truncatus) have long fascinated animal communication researchers due to their large brains and varied communicative signals. However, studying dolphin communication is challenging due to difficulties in identifying which individual is making a sound. A long-term study of a resident population of free-ranging dolphins in waters near Sarasota, Florida, employs brief catch-and-release as a research tool for health assessments, and this has enabled us to obtain high-quality recordings of known individual dolphins for 4 decades. We have a catalog of the individually distinctive signature whistles (SW) of most animals in the community; these referential signals function much like human names. Whistles other than the signature, known as “non-signature whistles” (NSW) are very poorly understood. We are building a catalog of stereotyped NSWs that are shared by more than one individual, and have so far identified more than 20 shared NSW types, two of which were produced by at least 25 different individuals. These whistles were recorded both during health assessments and from free-swimming dolphins wearing non-invasive, suction-cup attached digital acoustic tags (DTAGs), which we are able deploy on dolphins prior to release. We have embarked on playback studies to study the functions of both SW and shared NSW, in which we film movement responses with drones and record vocal responses with hydrophones and DTAGs. Control trials (n=21), in which we played the target dolphin’s own SW, elicited approach in 76% of trials in which we were able to observe the response. These data support the affiliative nature of SW copies, which appear to function as a way to initiate contact with another individual. Playbacks of a widely shared NSW, NSWA (n=8 trials), consistently elicited avoidance responses (100% of 6 observed trials) , suggesting an alarm or warning type function. Another widely shared NSW, NSWB, has elicited varying responses in 8 trials, depending on the age and sex of the target dolphin. NSWB was also produced by the target dolphin in response to 2 playback trials. Our suggested function of NSWB is a “query”- type whistle, produced when something unexpected or unfamiliar is heard. In this case, we would expect different responses depending on age and sex class, for example with males likely being more interested in exploring unfamiliar stimuli than females with calves. Overall, this research presents the first evidence for shared, stereotyped, context-specific whistles in bottlenose dolphins, and suggests that NSWs play an important role in the dolphin communication system.