COVID‐19 disruption reveals mass‐tourism pressure on nearshore sea turtle distributions and access to optimal breeding habitat

Abstract

Quantifying the extent to which animals detect and respond to human presence allows us to identify pressure (disturbance) and inform conservation management objectively; however, obtaining baselines against which to compare human impact is hindered in areas where human activities are already well established. For example, Zakynthos Island (Greece, Mediterranean) receives around 850,000 visitors each summer, while supporting an important loggerhead sea turtle rookery (~300 individuals/season). The coronavirus (COVID-19)-driven absence of tourism in May-June 2020 provided an opportunity to evaluate the distribution dynamics of this population in the absence (2020) vs. presence (2018 and 2019) of visitors using programmed unmanned aerial system (UAS) surveys. Ambient sea temperature transitioned from suboptimal for breeding in May to optimal in late June, with turtle distribution appearing to shift from shallow (to benefit from waters 3-5°C above ambient) to deeper waters in 2018 and 2019, but not 2020. The 2020 data set demonstrated that increased tourism pressure, not temperature, drives turtles offshore. Specifically, >50% of turtles remained within 100 m of shore at densities of 25-50 visitors/km, even when sea temperature rose, with 2018 and 2019 data supporting this trend. Reduced access to warmer, nearshore waters by tourism could delay the onset of nesting and increase the length of the egg maturation period between nesting events (internesting interval) at this site. A coastal refuge zone could be delimited in May-June where touristic infrastructure is minimal, but also where turtles frequently aggregate. In conclusion, sea turtles appear capable of perceiving changes in the level of human pressure at fine spatial and temporal scales and adjusting their distribution accordingly.

Human‐induced evolution: Signatures, processes and mechanisms underneath anthropogenic footprints on natural systems

“…However, most of the plasticity appears to be maladaptive: turbid conditions lead males to spend more time by the nest, contrary to female preferred behaviour such as increased search activity and time spent by the female. Comparable changes in behaviours during the reproductive period were also observed in sea turtles ( Caretta caretta ) nesting in Zakynthos (Greece), whereby the presence of tourists forces the turtles to use suboptimal, slightly cooler waters, that slow‐down egg development (Schofield et al, 2021 ). The impact is a likely longer nesting period, which may result in lower hatching success, ultimately selecting for faster development with unknown consequences.…”

“…The impact is a likely longer nesting period, which may result in lower hatching success, ultimately selecting for faster development with unknown consequences. The forced displacement of turtles was only visible because of the ban on travel related to the SARS‐CoV2 pandemic, which reduced the effects of tourist presence on turtle behaviours (Schofield et al, 2021 ).…”

Aerial Drones Reveal the Dynamic Structuring of Sea Turtle Breeding Aggregations and Minimum Survey Effort Required to Capture Climatic and Sex-Specific Effects

“…All UAS footage was reviewed manually by at least two independent observers. We recorded the longitude and latitude of each turtle detected on footage (accurate to within 55 cm; Dujon et al, 2021;Schofield et al, 2021), along with sex, behaviour, position in water column (i.e., seabed versus midwater, with midwater turtles having a shadow on the seabed), distance from shore and seabed depth. Previous field validation at the study site confirmed that the detection of turtles was reliably consistent at the surveyed depths and across surveys (Schofield et al, 2017).…”

A social media-based framework for quantifying temporal changes to wildlife viewing intensity: Case study of sea turtles before and during COVID-19

“…Social media records were collected for 2019, 2020 and 2021 following the methods described in Papafitsoros et al (2021). The first year represented a typical tourism year (2019) and the next two years (2020 and 2021) were heavily and mildly impacted by COVID-19, respectively, when tourism levels were limited by global travel restrictions (Schofield et al, 2021). Instagram was selected over other social media types because of its popularity and convenient search framework via "hashtags" and "places".…”

“…However, this demand (and consequent pressure) is not consistent within or across years (Moorhouse et al ., 2015), particularly in areas supporting seasonal migrants, such as breeding humpback whales and sea turtles. The recent COVID-19 pandemic exemplifies this issue via the unprecedented absence of ecotourism in hotspots globally, which provided new insights on animal behaviour and movement patterns in the absence of human disturbance (Rutz et al ., 2020; Bates et al ., 2021; March et al ., 2021; Schofield et al ., 2021). Even within the same population, animals are not randomly distributed in time or space, with certain individuals (in hotspots or residents) being disproportionately targeted (Semeniuk et al ., 2009; Christiansen and Lusseau, 2014).…”