American alligators (Alligator mississippiensis) are abundant large-bodied predators and occur in nearly every type of fresh and brackish water habitat across the southeastern United States [25]. The ecology of alligators residing in estuaries is well-studied, including their movement behavior in the coastal Everglades [15, 33, 34]. Given that coastal areas are subject to hurricanes, tropical storms, and other extreme weather events, alligators certainly experience impacts of these major disturbances. In the earliest account, Chabreck [7] observed that alligators were swept inland more than 16 km by Hurricane Audrey in 1957. Elsey and Aldrich [13] found a live juvenile alligator on a Louisiana beach after Hurricane Ike (2008) almost 500 km from its tagging site 8 weeks earlier. Another study suspected that storm surge in southwestern Louisiana after Hurricane Rita in 2005 pushed alligators inland [22]. These reports indicate that coastal alligators may be passively displaced by changing hydrology from major storms; however, no studies have revealed the direct movement responses of crocodilians to tropical cyclones [8, 13].
Though few studies have investigated how crocodilians respond to tropical cyclones, nearly all focus on negative effects on nesting success or passive displacement of alligators from storm surge and flooding. For instance, evidence indicates that tropical storms and hurricanes reduce nesting success and lead to hatchling mortality through flooding for both the American alligator and the American crocodile (Crocodylus acutus) [8, 21, 28, 30]. Contrary to many large-bodied animals, mortality rates via telemetry are difficult to obtain for crocodilians given that some individuals exhibit largely sedentary movement patterns [10, 34]. Nonetheless, we did not observe any indication of direct storm-related mortality typically signified by constant hourly detections at one station for an extended time. This is in contrast to apparent hurricane-related mortality events found in other large estuarine predators within Shark River Estuary, including juvenile bull sharks [36] and common snook [24] during Hurricane Irma. Given the ability of adult alligators to seek shelter on both land and water and their large and armored bodies, a major hurricane may be unlikely to cause mass direct mortalities of adult alligators.
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Alligators need regular access to low-salinity water for survival due to their lack of functioning salt glands and are physiologically limited in their distribution within coastal estuaries [12, 23]. Nonetheless, alligators in the Shark River Estuary exhibit considerable individual variation in movement behavior across the estuary and use several movement tactics including being residents of a particular habitat and exhibiting two forms of commuting: (1) making short trips from the mid-estuarine zone to freshwater areas and (2) undergoing regular but relatively brief long-distance travels downstream to exploit prey-rich marine food webs [33]. We observed each of these tactics within our subset of tracked animals. Four alligators remained in the upstream freshwater areas and marsh exclusively. One animal ranged across most of the estuary and two individuals used mid-estuary habitats and made regular long-distance trips to downstream areas. Lastly, we had one individual that shifted its behavior from remaining upstream exclusively to exhibiting commuting behavior to downstream foraging areas after the storm in September 2017 to our last download in January 2019. Our data indicate that the timing of the hurricane correlated with a shift from resident to commuter movement tactics for this animal. Within our Shark River Estuary population, there is considerable consistency in movement behaviors across years and no other alligator has been observed to switch general movement tactics [33, 34].
We saw variation in movement responses to Hurricane Irma by our tracked alligators, but two animals showed no discernable change in movements or habitat use throughout the study. The remaining six animals may have altered movement patterns or habitat use as a result of the hurricane. For instance, one animal remained slightly more upstream, used less of the estuary, and halted excursions to Tarpon Bay from mid-estuary for 8 months after the hurricane, which had been regular trips pre-hurricane. Another animal appeared to stop regular short trips upstream within Rookery Branch after the hurricane. Also, a different animal moved upstream from the lower river to Tarpon Bay immediately after the hurricane despite not doing this in the 60 d prior. It is possible that these changes were not related to the hurricane. Environmental conditions (e.g., dissolved oxygen and salinity regimes) remained altered for weeks after Hurricane Irma within the estuary [36] and could have changed the need for alligators to travel for food, thermoregulation, or osmoregulation. Two other alligators appeared to have moved from marsh and mangrove forest habitats to river channels soon after (2 days and 11 days) the hurricane strike. These findings mimic those of Chabreck [7], who observed alligators moving from marsh habitats to open water habitats like canals and bayous after Hurricane Carla in 1961. Seeking deeper water habitats to deal with increasing discharge, wave action, or rising water levels that follow tropical cyclones has been documented for several aquatic taxa [19, 24, 36]. Given that alligators are semi-aquatic air-breathing animals, it is unlikely that their response is one of seeking refuge from expected future disturbances. It is possible that these movements into river channels were not related to the hurricane, but we suspect that prey or carrion from the marsh and mangrove forest may have moved or been washed into the river channels from high inflow [14], with alligators responding to changes in food distribution.
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Avoid the crash: not having a daily risk download like what we provide subscribers with our proprietary FRISK score, when world events like armed conflict are changing industry every day, is like flying a plane without instruments through a hurricane.
Heavy rainfall (in moderation) can be beneficial for amphibians because it fills the temporary wetlands where they breed. Temporary wetlands are important for amphibian reproduction because they generally lack predators like large fish that would eat amphibian eggs and larvae. But the amount of rainfall and surge from a hurricane can be harmful to them. Excessive rainfall from major storms like Hurricane Ian cause those wetlands to become connected to larger bodies of water that may include additional predators.
The history behind encroach is likely to hook you in. The word derives from the Middle English encrochen, which means "to get or seize." The Anglo-French predecessor of encrochen is encrocher, which was formed by combining the prefix en- ("in") with the noun croche ("hook"). Croche also gave us our word crochet, in reference to the hooked needle used in that craft. Encroach carries the meaning of "intrude," both in terms of privilege or property. The word can also hop over legal barriers to describe a general advancement beyond desirable or normal limits (such as a hurricane that encroaches on the mainland). 2ff7e9595c
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