Inferring activity budgets in wild animals to estimate the consequences of disturbances

Abstract

Activity budgets can provide a direct link to an animal's bioenergetic budget and is thus a valuable unit of measure when assessing humaninduced nonlethal effects on wildlife conservation status. However, activity budget inference can be challenging for species that are difficult to observe and require multiple observational variables. Here, we assessed whether whalewatching boat interactions could affect the activity budgets of minke whales (Balaenoptera acutorostrata). We used a stepwise modeling approach to quantitatively record, identify, and assign activity states to continuous behavioral time series data, to estimate activity budgets. First, we used multiple behavioral variables, recorded from continuous visual observations of individual animals, to quantitatively identify and define behavioral types. Activity states were then assigned to each sampling unit, using a combination of hidden and observed states. Three activity states were identified: nonfeeding, foraging, and surface feeding (SF). From the resulting time series of activity states, transition probability matrices were estimated using first-order Markov chains. We then simulated time series of activity states, using Monte Carlo methods based on the transition probability matrices, to obtain activity budgets, accounting for heterogeneity in state duration. Whalewatching interactions reduced the time whales spend foraging and SF, potentially resulting in an overall decrease in energy intake of 42%. This modeling approach thus provides a means to link short-term behavioral changes resulting from human disturbance to potential long-term bioenergetic consequences in animals. It also provides an analytical framework applicable to other species when direct observations of activity states are not possible.

Marine vessels alter the behaviour of bottlenose dolphins Tursiops truncatus in the Istanbul Strait, Turkey

“…A reduction in feeding can lead to a decrease in energy intake (Christiansen et al 2013), while a decrease in resting is likely to reduce the energy reserves (Constantine et al 2004, Lusseau 2004. Over time, alterations to the dolphins' bioenergetic budget can lead to a decrease in body condition, which in turn can have negative effects on survival and reproductive success (New et al 2014, Christiansen & Lusseau 2015.…”

“…'Preceding' behavioural states (P ) essentially represent the first group behavioural state recorded (at t min time), and 'following' behavioural states (F ) represent the follow-up behavioural state (at t + 3 min time). Behavioural contingency tables (P vs. F ) were developed both for control and impact chains in order to investigate the temporal dependence between behavioural states (Lusseau 2003, Christiansen et al 2010, 2013, Meissner et al 2015. Control situation represented no vessels present (within 400 m of the focal group) between the preceding and following behavioural states.…”

“…Dusky dolphins Lagenorhynchus obscurus (Barr & Slooten 1999, Dans et al 2008, common dolphins Delphinus delphis (Stockin et al 2008, Meissner et al 2015, Indo-Pacific humpback dolphins Sousa chinensis (Van Parijs & Corkeron 2001), sperm whales Physeter macrocephalus (Gordon et al 1992), minke whales Balaenoptera acutorostrata (Christiansen et al 2013), Hector's dolphins Cephalorhynchus hectori (Bejder et al 1999) and bottlenose dolphins (Nowacek et al 2001, Hastie et al 2003, Lusseau 2004, Christiansen et al 2010, Pirotta et al 2015, Perez-Jorge et al 2017, have demonstrated both short-and longterm behavioural changes in response to marine vessels within a wide range of ecological settings. Such changes can take on various forms, with the most frequent being variations in vocalization, an increase in dive intervals, both vertical and horizontal avoidance behaviour, an increase in swimming speed, and a decrease in foraging and resting behaviour (Lusseau 2004, Stockin et al 2008, Christiansen et al 2010, 2013, Meissner et al 2015. By contrast, cases exist whereby habituation may be particularly advantageous to the population as a whole.…”

Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?

“…The degree to which this happens is currently an important question for cetacean conservation, in all species (e.g., Parsons et al, 2015). For example, even minor reductions in feeding behavior as the result of human disturbance were estimated to have dramatic effects on the energy budget of cetaceans, which could translate into substantive negative impacts on cetacean fitness and health (Christiansen et al, 2013).…”

Best Practice Framework and Principles for Monitoring the Effect of Coastal Development on Marine Mammals

“…Behavioral and/or physiological disturbance may also influence energetics (energy intake and expenditure), which over time can influence body condition, vital rates, and ultimately population dynamics (Christiansen and Lusseau, 2015;New et al, 2015). In such a scenario, monitoring can focus on select indicators such as behavioral response, body condition and vital rates (e.g., offspring production and survival) to vessel disturbance along with exposure and activity of vessels (e.g., Lusseau, 2004;Christiansen et al, 2013).…”