Michael Salmon

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• Ph. D.
• Professor at Florida Atlantic University

Marine turtles are visual animals, yet we know remarkably little about how they use this sensory capacity. In this study, our purpose was to determine whether loggerhead turtles could discriminate between objects on the basis of color. We used light-adapted hatchlings to determine the minimum intensity of blue (450 nm), green (500 nm), and yellow (...

Artificial lighting disrupts the nocturnal orientation of sea turtle hatchlings as they crawl from their nest to the ocean. Laboratory experiments in an arena were used to simultaneously present artificial light (that attracted the turtles toward “land”) and natural cues (a dark silhouette of the dune behind the beach) that promoted “seaward” orien...

1. General accounts of the natural history and behaviour of fiddler crabs suggest there exist two broad mating patterns in the genus. Most western and Indo‐Pacific species mate on the surface of intertidal substrates near burrows females defend. The sexes associate only briefly during courtship and mating. In contrast, males of many American specie...

Synopsis Here we describe examples of studies that have contributed both to a basic understanding of the biology of imperiled marine turtles, and to their management and conservation. Key elements include, first and foremost, correctly identifying species that differ strikingly in their morphology at different life stages because with growth, they...

This essay, written for the general public, describes the evidence that hatchling sea turtles are capable of navigation during their oceanic phase of development.

This essay, written for a general audience, describes the experiments that defined how hatchling marine turtles orient offshore during the beginning of their migratory adventures.

This essay provides background information of the status of endangered western Pacific leatherback sea turtles, and reviews the possibility of using head-starting as a strategy to promote their recovery.

This is Part 2 of a discussion that considers how best to recover severely threatened western Pacific leatherback marine turtles. Recent advances in our ability to captively rear this species, described by biologists from Thailand, indicate that "head-starting" may be an important component of that effort.

This essay describes, for a general audience, how built-in instincts for navigation promote the survival of hatchling sea turtles.

This article describes the impact of global warming on sea turtles, as well as the efforts being made by biologists to reduce that impact. The article will be published in the Environmental Outreach magazine. I hope you find it informative.

Sea turtles are vulnerable to climate change since their reproductive output is influenced by incubating temperatures, with warmer temperatures causing lower hatching success and increased feminization of embryos. Their ability to cope with projected increases in ambient temperatures will depend on their capacity to adapt to shifts in climatic regi...

This article is written to inform the general public about our attempts to recover world-wide populations of endangered and threatened marine turtles. It will soon be published in the Environmental Outreach magazine. I hope you find it of interest.

This essay describes a study, soon to be published in the Environmental Outreach magazine, showing that juvenile marine turtles grow wider faster than they grow longer. Doing so likely provides a survival advantage when the turtles encounter gape-limited predators. It is written for the general public in an effort to communicate how biologists go a...

In marine turtles it is well established that the shorter light wavelengths in the visible and near-ultraviolet spectrum provide more potent, and preferred , cues for nocturnal seafinding orientation than the longer light wavelengths. In this study, we simultaneously presented leatherback hatchlings (Dermochelys coriacea) with a short near-ultravio...

This article, written for the general public, summarizes the evidence published by others that marine turtles navigate by using a crude, but effective, map system.

This article, soon to be published in Environmental Outreach magazine, is written for a general audience and describes research adventures recently experienced in Hawai'i.

Schiariti, J.P. and Salmon, M., 0000. Impact of sargassum accumulations on loggerhead (Caretta caretta) hatchling recruitment in SE Florida, United States. Journal of Coastal Research, 00(0), 000-000. Coconut Creek (Florida), ISSN 0749-0208. Hatchling loggerhead turtles emerge from subsurface nests on oceanic beaches at night, then crawl toward and...

This poster describes how the study of basic biology leads to sometimes unforeseen advances in applied biological benefits to marine turtle conservation and management.

This poster describes an experimental approach to understanding how seafinding is accomplished by hatchling leatherback marine turtles.

After completing embryonic development, marine turtle hatchlings emerge from their subsurface nest, generally at night, and crawl to the ocean ('sea finding'). That response depends upon the ability of the turtles to discriminate between the brighter seaward versus a dimmer landward horizon, followed by a positive phototaxis. While the crawls of mo...

This article describes the negative impact of Sargassum blooms on sea turtle hatchling production at a nesting beach in SE Florida. It is written for a general audience and will soon be published in Environmental Outreach magazine.

The goal of this study was to determine whether marine turtle (loggerhead) embryos communicate with one another using mechanical cues detected through the flexible egg shell. In the process, the embryos might develop faster and hatch with greater synchrony (as occurs in some freshwater turtles). To find out, we performed experiments under controlle...

This essay is written for the general public. It describes how embryos within a turtle nest communicate with one another and, in the process, adjust their rate of development so as to hatch at about the same time. Doing so is believed to provide the hatchlings with survival advantages. The article will be published in Environmental Outreach magazin...

This is an article written for the general public, and soon to be published in our local magazine, Environmental Outreach. It is based upon a thesis completed by one of my Masters students (Shelby Hoover) who analyzed 33 years of data from a loggerhead nesting beach on Florida's West Coast (Keewaydin Island). It's rare to have access to so much lon...

This is an article written for the general public, and soon to be published in our local magazine, Environmental Outreach. It is based upon a thesis completed by one of my Masters students (Shelby Hoover) who analyzed 33 years of data from a loggerhead nesting beach on Florida's West Coast (Keewaydin Island). It's rare to have access to so much lon...

This essay is written for a general audience and will be published in Environmental Outreach magazine, some time this month.

This short essay is a tribute to my doctoral dissertation advisor, written shortly after his death. The experience of working with him served as a guide to me when the time came to mentor my students. It also portrays what to me are the essential qualities of an academic scientist whose important task is to train the next generation of scientists.

This is an article written for the public, and soon to be published in a local magazine, Environmental Outreach. I hope you enjoy it!

Invasive fire ants prey on a variety of organisms in the southeastern US, including the pipped eggs and hatchlings within sea turtle nests. The granular fire ant bait AMDRO® (active ingredient hydramethylnon) is currently used at some rookeries to protect nests, but no studies have been conducted to determine if the pesticide negatively impacts the...

Green turtles raised in the laboratory widen faster than they lengthen, thus changing in shape from the proportions they show as hatchlings. By doing so, young turtles may sooner achieve a size refuge from their gape-limited predators. In this study, we document that wild juveniles captured at open-water weed lines in the Gulf of Mexico show simila...

Every once in a while it seems appropriate to acknowledge the contributions of great naturalists and here, I pay tribute to my favorites, Karl von Frisch and Niko Tinbergen. They set the standards for how to study the behavior of animals in their natural world based upon an approach known as Ethology.

Hatchling marine turtles emerge at night from underground nests on oceanic beaches and then use visual cues to crawl from the nest site to the sea (“seafinding”). However, the light wavelengths (λ’s) used to accomplish this orientation have not been thoroughly documented, nor do we understand why some λ’s are favored over others. We measured noctur...

In this study, we compare and contrast armoring strategies during early ontogeny among three related species of marine turtles: the hawksbill, a species that diverged about 29 mya from the loggerhead and Kemp’s ridley, which diverged from one another about 16 mya. Our purpose was to determine whether there was a correlation between divergence time...

Many marine organisms (invertebrates, fishes) produce large numbers of small offspring (larvae) that differ in appearance and behavior from adults. That outcome occurs because larvae as they grow occupy one or more ontogenetic niches that select for phenotypes that differ from those that promote adult survival. Our purpose in this study was to dete...

Marine turtles produce hundreds of precocial offspring (“hatchlings”) that are virtually defenseless. Many are consumed by predators. Hatchlings improve their survival prospects by migrating to offshore “nursery” areas with lower predator densities and, as they grow, by developing morphological defenses. The flatback turtle (Natator depressus), how...

Marine turtles in the open ocean often forage in areas of enhanced productivity, but how they locate those sites and what they do once there is poorly understood. One possibility is that odors from prey might be informative. We explored those possibilities in laboratory experiments using juvenile marine turtles. We analyzed responses to an airborne...

Nesting populations of Critically Endangered hawksbill sea turtles remain depleted across much of their range in the Caribbean. Some islands, however, including Jumby Bay (Pasture Bay) in Antigua, have shown a steady increase in the number of nesting females. Furthermore, in recent years nesting has occurred in particularly high densities within th...

Marine turtles are large reptiles that compensate for high juvenile mortality by producing hundreds of hatchlings during a long reproductive lifespan. Most hatchlings are taken by predators during their migration to, and while resident in, the open ocean. Their survival depends upon crypticity, minimizing movement to avoid detection, and foraging e...

Juvenile green turtles (Chelonia mydas) differ in abundance on nearshore reefs, but why some sites are preferred over others is unknown. Our study had two objectives: to quantify site-specific differences in turtle abundance over time (1 y) and to determine what ecological factors were correlated with those differences. We conducted quarterly surve...

Across much of their range in the Caribbean, nesting populations of Critically Endangered hawksbill sea turtles remain depleted. Some islands, however, including Long Island (Pasture Bay) in Antigua, have shown a steady increase in the number of nesting females. However, in recent years nesting has occurred in particularly high densities within the...

Hatchling marine turtles show a nocturnal rhythm of emergence from the nest. Here, we highlight aspects of the rhythm that are incompletely understood, with special reference to differences in the rhythm's expression among populations as well as its cessation at dawn. We postulate that the rhythm ceases because the hatchlings, as they dig toward th...

Background/Question/Methods Female marine turtles lay thousands of eggs over a long reproductive life but only a small fraction of their offspring survive to adulthood. Most offspring mortality occurs during the earliest growth stages (hatchlings, juveniles) that survive in the open ocean by hiding until they become too large to be consumed. Many...

ABSTRACT: In numerous studies involving hatchling sea turtles, researchers have collected small numbers of hatchlings from nests a few hours before the turtles would otherwise have emerged naturally. This procedure makes it possible to do experiments in which the behavioral or physiological responses of numerous hatchlings must be tested in a limit...

Juvenile green turtles occupy home ranges on shallow reefs that parallel the southeastern coast of Florida. When disturbed, the turtles often flee eastward toward deeper water. We captured turtles at night and recorded their orientation during the next 2 days while they swam tethered inside a large circular outdoor pool and were exposed to the sun....

Loggerhead sea turtle hatchlings emerge from nests on either the east or west coast of the South Florida peninsula and then migrate offshore in opposite directions. Under laboratory conditions, magnetic cues induce east coast hatchlings to swim in directions that promote their transport by oceanic surface currents, such as the North Atlantic gyre....

The flatback turtle is the only species of marine turtle that lacks an oceanic phase of development in its early life history. Instead, the turtles grow to maturity in shallow turbid shelf waters of tropical to subtropical Australia. We studied the development of diving behavior in neonate flatbacks to determine whether diving under those ecologica...

Sea turtle hatchlings ernerge from underground nests, crawl to the ocean and swim out to sea. The orientation cues used to maintain offshore headings are unknown. Our field experiments suggest loggerhead hatchlings on the Atlantic coast of Florida continue on offshore headings by swimming into oceanic swells and wind-generated waves. Dependence on...

Adult rainbow and purple parrot fishes (Scarus guacamaia and S. coelestius) on the south shore of Bermuda live in offshore caves at night. During the day they feed along the shoreline. These fish, caught over the feeding grounds, when released in areas apparently unfamiliar to them, move in a southeasterly direction (90° to 180° of north) regardles...

ABSTRACT: Marine turtle hatchlings emerge from nests on oceanic beaches, crawl to the surf zone and migrate offshore. Predators in shallow water can take many hatchlings, but once the turtles reach deeper water, both encounters with predators and mortality rates probably decline. Behavioral studies have demonstrated that hatchlings show changes in...

We compared activity, diving behavior and response to prey by Dermochelys coriacea and Chelonia mydas during their first 8–10 weeks of development. We reared juveniles in the laboratory and, at two-week intervals, released them in the ocean for a brief trial. Each turtle towed a device used to measure its dive profile. All turtles swam throughout t...

Hatchling marine turtles emerge at night from underground nests, enter the ocean, and swim offshore. Here, we measured the intensity (hours swimming) and the temporal patterning (diurnal vs. nocturnal expression) of activity shown by Malaysian (Sulu Sea) hawksbill (Eretmochelys imbricata) and green turtle (Chelonia mydas) hatchlings tethered inside...

Previously, we showed that during their first six days of swimming hawksbill hatchlings are less active than the hatchlings of other marine turtle species. Here, we document that hawksbills also employ slower, drag-based swimming gaits during the brief periods when they do swim. These gaits may render the turtles less conspicuous to predators that...

Electroretinographic recordings were made from hatchling loggerhead and leatherback sea turtle eyecup preparations during presentation of sinusoidally modulated lights of different frequencies, mean intensities and colors. Cross-correlation analysis was performed to determine the extent to which the responses followed the intensity modulated light...

Larval release by adult fiddler crabs occurs during the ebbing tides, but its timing relative to the day-night and tidal amplitude cycles depends upon tidal form, e.g., shows phenotypical plasticity. Crabs (Uca thayeri) from Florida's East Coast are exposed to semidiurnal tides and release their larvae at night, whereas crabs from Florida's West Co...

The South Florida subpopulation of loggerhead sea turtles (Caretta caretta L.) nests with great fidelity on either the southeast or the southwest coast of Florida, USA. The hatchlings that emerge from those nests must swim in opposite directions and search for different surface currents to migrate away from continental shelf waters. In this laborat...

Electroretinographic recordings were made from hatchling loggerhead and leatherback sea turtle eyecup preparations to generate dark-adapted spectral sensitivity curves. Both species were maximally sensitive to wavelengths between 500 and 540 nm, with a secondary peak near 380 nm. The spectral sensitivity curve for leatherbacks was attenuated at the...

ABSTRACT: Sea turtles are injured and sometimes killed because of interactions with pelagic longlines, such as hook ingestion, entanglement in the lines, and forced submergence. Stimuli from bait, gear and lights (often used at night on swordfish lines) might attract sea turtles. Previous experiments with loggerheads Caretta caretta demonstrated th...

Amphibians and reptiles have evolved with natural lighting cycles. Consequently, alteration of natural variation in diurnal and nocturnal light intensities and spectral properties has the potential to disrupt their physiology, behavior, and ecology. We review the possible effects of night lighting on many species of amphibians and reptiles, noting...

Artificial lighting disrupts sea turtle hatchling orientation from the nest to the sea. We studied how a light-induced landward crawl affects the later ability of hatchlings to crawl to the sea, and to swim away from the shore from a dark beach. A brief (2 min) landward crawl had no effect on swimming orientation as long as surface waves were prese...

On many nesting beaches, hatchling marine turtles are exposed to poled street lighting that disrupts their ability to crawl to the sea. Experiments were done to determine how hatchlings responded to street lighting transmitted through 2 filters that excluded the most disruptive wavelengths (those < 530 nm; those < 570 nm). Filtered lighting, howeve...

Street lighting on coastal roadways is often visible at sea turtle nesting beaches, and disrupts the nocturnal orientation of hatchlings as they crawl toward the sea. Our objective was to determine whether an alternative lighting system (light-emitting diodes, embedded in the roadway pavement) prevented orientation disruption. Hatchlings at the bea...

Many animals, including sea turtles, alter their movements and home range in relation to the particular type and quality of the habitat occupied. When sufficient resources are available, individuals may develop affinities to specific areas for activities, such as foraging and (or) resting. In the case of green sea turtles (Chelonia mydas L.), after...

Natural transitions between light and darkness influence the biology and behaviour of many organisms. What happens when humans introduce light into darkness? Oceanic beaches, where sea turtles nest, provide an example of both the problem and approaches to its solution.

We raised leatherback posthatchlings in the laboratory for up to 7 weeks to study the role of visual and chemical cues in food recognition and food-seeking behavior. Turtles were reared on a formulated (artificial gelatinous) diet and had no contact with test materials until experiments began. Subjects were presented with visual cues (a plastic jel...

Intraocular recordings were made from the eyestalks of dark-adapted fiddler crabs (Uca thayeri) during presentation of monochromatic light flashes of different wavelengths and intensities. Two types of signals were recorded in different experiments: slow potentials (electroretinogram) and fast potentials (spikes). The latter were also recorded in t...

Fiddler crabs (Uca thayeri) on Florida's east and west coasts show temporally distinct hatching rhythms, correlated with differences in tidal form. Our purpose in this study was to determine whether these differences were fixed or could change in response to variation in the tides. West coast crabs (but not east coast crabs) showed seasonal variati...

We compared the timing of larval release by Ucathayeri exposed to different tidal regimes. Crabs on Florida's East Coast experience semidiurnal tides, whereas crabs on the Florida's West Coast experience mixed tides.In both populations, hatching occurred shortly after high tide. On the East Coast, most crabs released their larvae between dusk and m...

This paper reviews behavioral, physiological, anatomical, and ecological aspects of sound and vibration detection by decapod crustaceans. Our intent is to demonstrate that despite very limited work in this area in the past 20 years, evidence suggests that at least some decapod crustaceans are able to detect and use sounds in ways that parallel dete...

The eyes of three species of sea turtle hatchlings (loggerheads, green turtles, and leatherbacks) possess visual streaks, areas of densely packed ganglion cells running along the antero‐posterior retinal axis. These probably function to provide heightened visual acuity along the horizon. The vertical extent and absolute concentration of cells withi...

Leatherback hatchlings are difficult to maintain under captive conditions because they (i) suffer from bacterial and fungal infections when water quality is poor (Frayr 1970) and (ii) are dietary specialists (Bjorndal 1997). Leatherbacks (iii) do not recognize physical barriers (Witham 1977) and can abrade their skin (leading to infections) by swim...

All sea turtle nests at Boca Raton, Palm Beach Co., Florida, U.S.A., are epowsed to foot traffic from visitors that use the beach, and to predators (raccoons, foxes, and sknks) that feed upon the egg and hatchlings of marine turtles. To protect the nests, managers have covered them with square wire cages anchored in the sand. We compared the fate o...

The effects of beach renourishment on a major marine turtle nesting beach (Jupiter Island) in Florida were studied over seven years. This made possible a long-term comparison between reproductive activity on several beaches, renourished at different times, and a control beach composed of natural sand. Our goal was to determine if renourishment resu...

Hatchling sea turtles emerge from underground nests, crawl to the ocean, and swim away from the land. In shallow water near shore, hatchlings maintain offshore headings by swimming into oceanic waves; in deeper water, however, turtles appear to rely on different mechanisms to maintain their courses. To determine whether loggerhead hatchlings, Caret...

Hatchling sea turtles generally emerge from nests at night and crawl immediately toward the ocean ("seafinding orientation"). On natural, dark beaches their orientation is usually appropriate, but where oceanfront buildings are present, hatchlings may crawl toward artificial lighting behind the beach. A systematic survey during the 1993 nesting sea...

Loggerhead sea turtles nesting in Florida sometimes deposit their clutches on urban beaches, This study was undertaken at a city beach to determine correlations between physical variables and where nests were placed. Over a four year period, the distribution of nests on the beach was statistically identical. Nesting density variation at particular...

At several locations on an urban nesting beach, loggerhead hatchlings emerging from their nests did not orient toward the sea. The cause was city lighting which disrupted normal seafinding behavior. Observations and experiments were conducted to determine why females nested where hatchlings were exposed to illumination, and how hatchlings responded...

Summary Recent experiments have demonstrated that hatchling loggerhead sea turtles can orient using the earth's magnetic field. To investigate the functional characteristics of the loggerhead magnetic compass, we tested the orientation of hatchlings tethered inside a circular arena surrounded by a coil system that could be used to reverse the verti...