Linking Behavior to Vital Rates to Measure the Effects of Non‐Lethal Disturbance on Wildlife

Abstract

The need for managing non-lethal effects on wildlife is becoming increasingly important as global human-wildlife interactions are now more frequent and more diverse. We developed a mechanistic model for minke whales (Balaenoptera acutorostrata) to measure the effects of behavioral disturbances caused by whalewatching activities on fetal growth. The model illustrates the pathway through which behaviorally mediated effects of anthropogenic disturbance might influence female reproductive success in an iteroparous capital breeding mammal. We found that although the behavioral disruptions caused by whalewatching interactions were substantial, the cumulative exposure of individuals to whalewatching boats was low, resulting in an effect on fetal growth no different from natural variability. This highlights the importance of considering all aspects of disturbance when evaluating effects of human disturbance on wildlife. Our mechanistic model can also be used to simulate different management scenarios to predict the long-term consequence of disturbance on vital rates, to help inform management decisions.

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. Socialising plays an important role for the dolphins' reproductive success and disruption to this behaviour could lead to a lower pregnancy rate, thus fewer offspring, which could have long-term negative biological consequences for the population (Lusseau 2004, 2006.…”

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

“…The type of risk, whether direct or indirect and lethal or sublethal, will influence the pathway and number of parameters needed to evaluate the consequences of that risk (Christiansen and Lusseau, 2015). For example, vessel traffic can have both direct and indirect effects on marine mammal populations.…”

“…To quantify this effect, direct observations, reporting or model simulation can be used. 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).…”

“…Currey et al, 2007Currey et al, , 2009Christiansen and Lusseau, 2015 Declines in physical health through, e.g., pollutant levels, injury or mortality rates -Increase in the incidence of mortalities and injuries of marine mammals Knowlton and Kraus, 2001;Panigada et al, 2006;Litz et al, 2007;Bechdel et al, 2009;Cagnazzi et al, 2013a,b *Potential trigger points will vary with between species and conservation status.…”

“…Such exposure can lead to many direct and indirect impacts including; temporary or permanent movement away from core habitats (Watson-Capps and Mann, 2005;Bejder et al, 2006b), disturbance to critical behaviors resulting in alterations to energy budgets and vital rates (Steckenreuter et al, 2011;Christiansen and Lusseau, 2015), increases in fishing interactions (Read, 2008;Mannocci et al, 2012;Allen et al, 2014), depletion in prey availability and increased competition for resources (Harwood, 2001), entanglement and ingestion of foreign debris (Harcourt et al, 1994;Page et al, 2004), disruption to acoustic communication systems with possible physiological damage to hearing abilities [Temporary Threshold Shift (TTS) and Permanent Threshold Shift (PTS)] (Richardson et al, 1995;Foote et al, 2004;Tyack, 2008;de Souza Albuquerque and da Silva Souto, 2013), increases in injury and mortality from vessel strikes (Wells and Scott, 1997;Laist et al, 2001;Panigada et al, 2006), bioaccumulation of toxins leading to immunosuppressant symptoms (Jepson et al, 2005;Litz et al, 2007;Cagnazzi et al, 2013a), reproductive collapse (Jepson et al, 2016), cerebral impairment (Cook et al, 2015), incidence of disease (Van Bressem et al, 1999) and the introduction of new parasites and pathogens (Delport et al, 2014(Delport et al, , 2015. The effect of these impacts upon populations of marine mammals, particularly where cumulative pressures are present, can lead to population-level consequences resulting in long-term shifts in habitat suitability, lower reproductive success, decreased health, increased mortality and population declines (Zhang et al, 2003;Lusseau, 2004;Wang et al, 2006;Bejder et al, 2006b;…”