A bioenergetics model to evaluate demographic consequences of disturbance in marine mammals applied to gray whales

Villegas‐Amtmann, Stella; Schwarz, Lisa; Sumich, James L.; Costa, Daniel P.

doi:10.1890/es15-00146.1

Cited by 92 publications

(138 citation statements)

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“…We estimated the total energetic requirements for an adult female WGW to survive and migrate from the feeding to the breeding grounds successfully reproducing upon her return (Villegas-Amtmann et al 2015). We estimated the magnitude of annual energy loss that would affect reproduction, offspring care, and survival.…”

Section: Methodsmentioning

confidence: 99%

“…Female gray whale energetic demands were parsed into 3 categories: (1) field meta bolic rate (FMR), reflecting energy requirements for maintenance at different activity levels and reproductive stages; (2) pregnancy costs; and (3) lactation costs, consisting of calf maintenance or metabolic rate and calf growth costs from 0−6.5 or 6.6 mo of age (weaning age). Energy requirements for 9 stages were based on the 3 reproductive phases from above: (i) foraging grounds (pregnant), (ii) foraging grounds (non-pregnant), (iii) southbound migration (pregnant), (iv) breeding lagoons (lactating), (v) (Rice & Wolman 1971, Villegas-Amtmann et al 2015. Timing and duration of female stages were obtained from satellite tracks and behavioral studies of the WGW population at their foraging grounds (Sy chenko 2011, Mate et al 2015, assuming they are migrating from Sakhalin Island, Russia, to BajaC.…”

Section: Methodsmentioning

confidence: 99%

“…where 0.0200 is the amount of heat produced in MJ l −1 O 2 consumed, from Kleiber (1961), %O 2 is the oxygen extraction efficiency per breath, T s the number of days in that stage, R s is respiration rate in breaths d −1 , and V t is tidal lung volume in l (Villegas- Amtmann et al 2015). Calf FMR was similarly estimated for each of 3 preweaning calf stages (used to estimate lactation costs) for BajaC calving grounds: breeding lagoons (0− 2.1 mo old), northbound migration (2.1−5.4 mo old), and foraging grounds (5.4−6.6 mo old) and for China calving grounds: breeding lagoons (0−3.4 mo old), northbound migration (3.4−5.3 mo old), and foraging grounds (5.3−6.5 mo old).…”

Section: Gray Whale Female Energetic Demandsmentioning

confidence: 99%

“…The model assumes that a biologically significant disturbance will cause changes in behavior resulting in reductions of net energy intake, compromising maternal condition, leading to reduced fecundity, energy delivery to offspring, offspring survival, and when high enough, increased adult mortality (NRC 2005, Costa 2012, New et al 2013, 2014. Following that framework, Villegas-Amtmann et al (2015) created a bioenergetics model for EGW females using a 2 yr reproductive cycle, and identified the demographic consequences of lost energy under possible disturbance scenarios. Disturbance while the female is pregnant is the first potential impact on future gray whale populations.…”

Section: Introductionmentioning

confidence: 99%

“…We extended the model of Villegas-Amtmann et al (2015) to calculate WGW energy requirements for a 2+ yr reproductive cycle and for 2 possible breeding grounds: (1) western Pacific, around Hainan Island in the South China Sea, and (2) eastern Pacific in the lagoons of Baja California, Mexico. We compared energy requirements between EGW and WGW populations and between both WGW breeding sites.…”

Section: Introductionmentioning

confidence: 99%

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East or west: the energetic cost of being a gray whale and the consequence of losing energy to disturbance

Villegas‐Amtmann¹,

Schwarz²,

Gailey³

et al. 2017

Endang. Species. Res.

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Western gray whales (WGW) Eschrichtius robustus are considered one of the world's most endangered baleen whale populations. Development of oil and gas fields in northeastern Sakhalin, Russia, is a concern, because they overlap with WGW feeding grounds. Some WGW migrate ~10 000 km from feeding grounds around Sakhalin Island (Russia), to breeding grounds in Baja California (BajaC; Mexico) and possibly ~6000 km to the South China Sea (China). We developed a WGW female bioenergetics model to examine potential consequences of energy lost from foraging cessation caused by anthropogenic disturbance, and compared it to eastern gray whales (EGW). Energy loss was then linked to potential reductions in reproduction and survival. Mean total energy requirements were 11 and 15% greater for WGW breeding in BajaC and China, respectively, compared to EGW, due to longer migration distance (25%) to BajaC and higher metabolic rates at foraging grounds. However, this difference is minimal for EGW that use the northern extent of their foraging range. On average, WGW breeding in BajaC and China need 9 and 17% more energy for survival than EGW. Our model predicts that WGW mortality would likely occur at 38 to 40% annual energetic loss. Long-term yearly energy loss of < 30% would reduce population growth due to lower reproductive rates. Ongoing yearly energy losses of > 30% would result in adult female mortality the first year, followed by lower reproductive rates of survivors. Our model suggests that energy losses of > 30% caused by disturbance should be considered a threshold for concern for this Critically Endangered population.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Gray Whale Female Energetic Demandsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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East or west: the energetic cost of being a gray whale and the consequence of losing energy to disturbance

Villegas‐Amtmann¹,

Schwarz²,

Gailey³

et al. 2017

Endang. Species. Res.

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Longer migration not necessarily the costliest strategy for migrating humpback whales

Riekkola

Andrews‐Goff

Friedlaender

et al. 2020

Aquatic Conservation

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Long‐distance migration is a demanding physical activity, and how well animals manage the associated costs will have important implications for their fitness. The Oceania humpback whale (Megaptera novaeangliae) population is recovering from past exploitation markedly slower than the neighbouring east Australian whales. The reasons for this are unknown, although higher energetic costs of longer migratory distances could be a possible explanation. Due to their fully aquatic lives, studying the energy expenditure of these large animals requires methods that do not rely on capturing the animal, such as bioenergetic models. A state‐space model was fitted to satellite data to infer behavioural states for southern migrating whales. Travel speeds and behavioural states were used in a bioenergetic model to estimate the energetic cost of the migration phase. Relative differences in average duration, distance, and energetic costs were compared between migratory routes and distances. Total energy used during migration was a trade‐off between cost of transport (determined by travel speed) and daily maintenance (determined by daily basal metabolic costs). Oceania whales migrating to the Amundsen and Bellingshausen Seas travelled fastest and furthest, 15 and 21% further than whales migrating to the d'Urville Sea (east Australian whales) and Ross Sea, respectively. Therefore, they had the highest cost of transport, 25 and 85% higher than for d'Urville Sea and Ross Sea whales, respectively. However, energy saved in terms of daily maintenance by using fewer days to complete a longer migration resulted in only a 6–7% increase in total energetic cost. The results highlight that travelling further does not necessarily translate into an increase in total energy expenditure for migratory whales, since they can compensate for longer distance by travelling faster. Further research on the energetics of different whale populations could provide insight into the productivity of Southern Ocean feeding regions and help understand the environmental and anthropogenic effects on the whales' energy budgets.

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Bio‐energetic modeling of medium‐sized cetaceans shows high sensitivity to disturbance in seasons of low resource supply

Hin

Harwood

Roos

2019

Ecological Applications

108

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Understanding the full scope of human impact on wildlife populations requires a framework to assess the population‐level repercussions of nonlethal disturbance. The Population Consequences of Disturbance (PCoD) framework provides such an approach, by linking the effects of disturbance on the behavior and physiology of individuals to their population‐level consequences. Bio‐energetic models have been used as implementations of PCoD, as these integrate the behavioral and physiological state of an individual with the state of the environment, to mediate between disturbance and biological significant changes in vital rates (survival, growth, and reproduction). To assess which levels of disturbance lead to adverse effects on population growth rate requires a bio‐energetic model that covers the complete life cycle of the organism under study. In a density‐independent setting, the expected lifetime reproductive output of a single female can then be used to predict the level of disturbance that leads to population decline. Here, we present such a model for a medium‐sized cetacean, the long‐finned pilot whale ( Globicephala melas ). Disturbance is modeled as a yearly recurrent period of no resource feeding for the pilot whale female and her calf. Short periods of disturbance lead to the pre‐weaned death of the first one or more calves of the young female. Higher disturbance levels also affect survival of calves produced later in the life of the female, in addition to degrading female survival. The level of disturbance that leads to a negative population growth rate strongly depends on the available resources in the environment. This has important repercussion for the timing of disturbance if resource availability fluctuates seasonally. The model predicts that pilot whales can tolerate on average three times longer periods of disturbance in seasons of high resource availability, compared to disturbance happening when resources are low. Although our model is specifically parameterized for pilot whales, it provides useful insights into the general consequences of nonlethal disturbance. If appropriate data on life history and energetics are available, it can be used to provide management advice for specific species or populations.

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A bioenergetics model to evaluate demographic consequences of disturbance in marine mammals applied to gray whales

Cited by 92 publications

References 58 publications

East or west: the energetic cost of being a gray whale and the consequence of losing energy to disturbance

East or west: the energetic cost of being a gray whale and the consequence of losing energy to disturbance

Longer migration not necessarily the costliest strategy for migrating humpback whales

Bio‐energetic modeling of medium‐sized cetaceans shows high sensitivity to disturbance in seasons of low resource supply

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