Predation (Biology)

Following nest emergence, sea turtle hatchling dispersal can be disrupted by
artificial light or skyglow from urban areas. Mis- or disorientation increases exposure to
predation, thermal stress, and dehydration, could consume valuable energy, and thus
influence the likelihood of survival. This study utilized laboratory simulations of
extended crawl distances and field observations to investigate the energy cost of
disorientation crawling on loggerhead (Caretta caretta) and green (Chelonia mydas) sea
turtle hatchlings and the impact on the subsequent swim frenzy. Extended crawls
increased oxygen consumption, decreased plasma glucose, and reduced green hatchling
swim performance following a 200m crawl. Surprisingly, plasma lactate concentrations
did not increase with crawl distance, likely due to frequent rest periods that would,
however, increase time on the beach and thus exposure to predators. This research may
provide managers with physiological data to determine best practices for sea turtle
conservation and adds to the biological knowledge of these animals.

Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops
truncatus) are two sympatric species resident to the Bahamas. The visibility of the
Bahamian water provided a unique opportunity to study spotted dolphin communication
during aggression. This study’s main focus was to decipher any similarities or differences
in the behaviors used by spotted dolphins during interspecific and intraspecific
aggression. Both similarities and differences were discovered. Biting, following, and
chasing behavioral events were used more during interspecific aggression, while the
display behavioral class was used more than the contact behavioral class during intrabut
not interspecific aggression. This study showed that spotted dolphins use more energy
intensive and risky behaviors when fighting interspecifically. This could result from
having to fight and defend females from a larger species, trying to avoid sexual
harassment from bottlenose males, or needing to use behaviors that are more overt and easily understood during interspecies communication.

The Argentine black and white tegu, Salvator merianae, is a nonnative species that has invaded parts of Florida. The potential impacts of this species on native Florida wildlife are not yet known. This study looks at the stomach contents of 169 S. merianae captured between 2011 and 2013 in south Florida to infer potential impacts of S. merianae and spatial or seasonal shifts in diet. Analysis of 169 GI tracts showed that S. merianae is an omnivorous, terrestrial forager with a broad dietary range which includes insects, fruits, plants, snails, crayfish, carrion, birds, small mammals, turtles, snakes, lizards, frogs and eggs. S. merianae diet composition varied with capture habitat, the fattest tegus were collected from disturbed/agricultural areas and these samples contained, primarily, gastropods and insects. Tegu dietary habits threaten local endangered and state listed species such as the American crocodile, Crocodylus acutus, and the Cape Sable seaside sparrow, Ammodramus maritimus mirabilis. Dedicated funds and efforts need to be focused on this species to limit its further spread and future impact on native species.

Invasive species are one of the major threats to biodiversity and understanding the effects any one invasive species has on members of its new ecosystem can help land managers decide how to best use their limited resources. This study attempted to show the effect Cuban Treefrogs (Osteopilus Septentrionalis) were having on native Florida hylids. For a year, Cuban Treefrogs were removed from three cypress domes and monitored in three other cypress domes, a change in the native population in the experimental domes was the eventual desired effect. Due to weather issues and low native hylid numbers no effect was shown, however due to environmental constraints an effect could not be ruled out either.

This dissertation examined the natal origins, home-range, and in-situ foraging behavior of an aggregation of sub-adult hawksbill turtles (Eretmochelys imbricata) found off the coast of Palm Beach County, Florida. Surveys were conducted on approximately 30 linear km of reef between 15 and 30 m in depth. Tissue samples were retrieved from 112 turtles for mtDNA haplotype determination. GPS-linked satellite transmitters were deployed on six resident sub-adults, resulting in both minimum convex polygon (MCP) and 95%, 50%, and 25% kernel density estimates (KDE) of home-range size. A foraging ethogram was developed, and sequential analysis performed on thirty videos (141 total minutes) of in-situ foraging behavior. Seventeen total haplotypes were identified in this aggregation, the majority (75%) of which represented rookeries on Mexico’s Yucatan Peninsula. Other sources, from most to least important, include Barbados, Costa Rica, Puerto Rico, Antigua, and the U.S. Virgin Islands.

The cues used by marine turtles to locate foraging areas in the open ocean are largely
unknown though some species (especially the green turtle [Chelonia mydas], the
loggerhead [Caretta caretta], and the leatherback [Dermochelys coriacea]) somehow
locate areas of high productivity. Loggerheads can detect airborne odors, but a capacity
to orient has not yet been investigated. In this comparative study, tethered loggerheads
and leatherbacks were exposed to dimethyl sulfide (DMS) or food odors in a laminar
flow of air. Turtles did not orient into the air current. Free-swimming loggerheads and
green turtles were also exposed to air- or waterborne food (squid) odor plus a neutral
visual stimulus. Both species showed increases in swimming activity and biting behavior
to both stimuli. These results suggest that airborne odors are likely not used to locate
distant areas, but that they are used in localized food searching efforts.

The sea anemone Aiptasia pallida is a biological model for anthozoan research.
Like all cnidarians, A. pallida possesses nematocysts for food capture and defense.
Studies have shown that anthozoans, such as corals, can rapidly increase nematocyst
concentration when faced with competition or predation, suggesting that nematocyst
production may be an induced trait. The potential effects of two types of tissue damage,
predator induced (Lysmata wurdemanni) and artificial (forceps), on nematocyst
concentration was assessed. Nematocysts were identified by type and size to examine the
potential plasticity associated with nematocyst production. While no significant
differences were found in defensive nematocyst concentration between shrimp predation
treatments versus controls, there was a significant difference in small-sized nematocyst in
anemones damaged with forceps. The proportions of the different types of nematocysts between treatment types were also found to be different suggesting that nematocyst
production in A. pallida is a plastic trait.

Marine turtles produce many offspring which offsets the high mortality
experienced by turtles during early development. Juvenile mortality might be reduced by
evolving effective behavioral as well as morphological anti-predator defenses. Body
proportions of three species (Caretta caretta, Chelonia mydas, Dermochelys coriacea) of
turtles were measured in the first fourteen weeks of development to examine how growth
may mitigate predation by gape-limited predators. Growth was categorized as isometric
if shape did not change during development or allometric if body shape did change. All
three species showed allometric growth in carapace width; however it was less
pronounced in the larger D. coriacea turtles. Allometric growth in carapace width
decreased as all three species grew in size. When high predation occurs in early
development, many species will favor rapid growth into a size refuge. Juvenile sea turtles
may optimize their survival by growing allometrically when predation risk is the greatest.