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East Falmouth, MA, United States

van Staaden M.J.,Bowling Green State University | Searcy W.A.,University of Miami | Hanlon R.T.,Marine Resources Center
Advances in Genetics

From psychological and sociological standpoints, aggression is regarded as intentional behavior aimed at inflicting pain and manifested by hostility and attacking behaviors. In contrast, biologists define aggression as behavior associated with attack or escalation toward attack, omitting any stipulation about intentions and goals. Certain animal signals are strongly associated with escalation toward attack and have the same function as physical attack in intimidating opponents and winning contests, and ethologists therefore consider them an integral part of aggressive behavior. Aggressive signals have been molded by evolution to make them ever more effective in mediating interactions between the contestants. Early theoretical analyses of aggressive signaling suggested that signals could never be honest about fighting ability or aggressive intentions because weak individuals would exaggerate such signals whenever they were effective in influencing the behavior of opponents. More recent game theory models, however, demonstrate that given the right costs and constraints, aggressive signals are both reliable about strength and intentions and effective in influencing contest outcomes. Here, we review the role of signaling in lieu of physical violence, considering threat displays from an ethological perspective as an adaptive outcome of evolutionary selection pressures. Fighting prowess is conveyed by performance signals whose production is constrained by physical ability and thus limited to just some individuals, whereas aggressive intent is encoded in strategic signals that all signalers are able to produce. We illustrate recent advances in the study of aggressive signaling with case studies of charismatic taxa that employ a range of sensory modalities, viz. visual and chemical signaling in cephalopod behavior, and indicators of aggressive intent in the territorial calls of songbirds. © 2011 Elsevier Inc. Source

Akkaynak D.,Massachusetts Institute of Technology | Hanlon R.T.,Marine Resources Center
Sea Technology

Every COTS digital camera captures images in its own RGB (red, green and blue) color space. Transforming these images to a device-independent color space is done through a transformation matrix. For land photography, the transformation from the camera color space to human color space is usually done through the use of photographic calibration targets, such as a Macbeth ColorChecker. Transforming raw images recorded by COTS digital cameras to a device- independent color space is usually done through a three-by-three transformation matrix that relates the camera color space to the human color space. While cameras have built-in software that perform this transformation, they do so without the knowledge of the colors in the scene, the ambient light conditions or the specific sensor in the camera. Colors will only be as accurate as the color transformation matrix. The CIE 1931 XYZ color space is commonly used as a device-independent space into which camera RGB values are mapped. Source

Crook R.J.,University of Houston | Lewis T.,Vassar College | Hanlon R.T.,Marine Resources Center | Walters E.T.,University of Houston
Journal of Experimental Biology

Survivable injuries are a common yet costly experience. The ability to sense and respond to noxious stimuli is an almost universal trait, and prolonged behavioral alterations, including sensitization to touch and other stimuli, may function to ameliorate fitness costs associated with injury. Cephalopods can modify their behavior by learned association with noxious electric shock, but nonassociative alterations of behavioral responses after tissue injury have not been studied. The aim of this study was to make the first systematic investigations in any cephalopod of behavioral responses and alterations elicited by explicit, minor injury. By testing responsiveness in the longfin squid, Loligo pealeii, to the approach and contact of an innocuous filament applied to different parts of the body both before and after injury to the distal third of one arm, we show that a cephalopod expresses behavioral alterations persisting for at least 2 days after injury. These alterations parallel forms of nociceptive plasticity in other animals, including general and site-specific sensitization to tactile stimuli. A novel finding is that hyper-responsiveness after injury extends to visual stimuli. Injured squid are more likely to employ crypsis than escape in response to an approaching visual stimulus shortly after injury, but initiate escape earlier and continue escape behaviors for longer when tested from 1 to 48?h after injury. Injury failed to elicit overt wound-directed behavior (e.g. grooming) or change hunting success. Our results show that longlasting nociceptive sensitization occurs in cephalopods, and suggest that it may function to reduce predation risk after injury. © 2011. Published by The Company of Biologists Ltd. Source

Mooney T.A.,Marine Resources Center | Lee W.-J.,Woods Hole Oceanographic Institution | Hanlon R.T.,Marine Resources Center
Marine and Freshwater Behaviour and Physiology

Cephalopods, and particularly squid, play a central role in marine ecosystems and are a prime model animal in neuroscience. Yet, the capability to investigate these animals in vivo has been hampered by the inability to sedate them beyond several minutes. Here, we describe methods to anesthetize Doryteuthis pealeii, the longfin squid, noninvasively for up to 5h using a 0.15 mol magnesium chloride (MgCl2) seawater solution. Sedation was mild, rapid (<4min), and the duration could be easily controlled by repeating anesthetic inductions. The sedation had no apparent effect on physiological evoked potentials recorded from nerve bundles within the statocyst system, suggesting the suitability of this solution as a sedating agent. This simple, long-duration anesthetic technique opens the possibility for longer in vivo investigations on this and related cephalopods, thus expanding potential neuroethological and ecophysiology research for a key marine invertebrate group. © 2010 Taylor & Francis. Source

Staudinger M.D.,University of North Carolina at Wilmington | Hanlon R.T.,Marine Resources Center | Hanlon R.T.,Brown University | Juanes F.,University of Massachusetts Amherst
Animal Behaviour

Longfin squid, Loligo pealeii, were exposed to two predators, bluefish, Pomatomus saltatrix, and summer flounder, Paralichthys dentatus, representing cruising and ambush foraging tactics, respectively. During 35 trials, 86 predator-prey interactions were evaluated between bluefish and squid, and in 29 trials, 92 interactions were assessed between flounder and squid. With bluefish, squid predominantly used stay tactics (68.6%, 59/86) as initial responses. The most common stay response was to drop to the bottom, while showing a disruptive body pattern, and remain motionless. In 37.0% (34/92) of interactions with flounder, squid did not detect predators camouflaging on the bottom and showed no reaction prior to being attacked. Squid that did react, used flee tactics more often as initial responses (43.5%, 40/92), including flight with or without inking. When all defence behaviours were considered concurrently, flight was identified as the strongest predictor of squid survival during interactions with each predator. Squid that used flight at any time during an attack sequence had high probabilities of survival with bluefish (65%, 20/31) and flounder (51%, 18/35). The most important deimatic/protean behaviour used by squid was inking. Inking caused bluefish to startle (deimatic) and abandon attacks (probability of survival = 61%, 11/18) and caused flounder to misdirect (protean) attacks towards ink plumes rather than towards squid (probability of survival = 56%, 14/25). These are the first published laboratory experiments to evaluate the survival value of antipredator behaviours in a cephalopod. Results demonstrate that squid vary their defence tactics in response to different predators and that the effectiveness of antipredator behaviours is contingent upon the behavioural characteristics of the predator encountered. © 2010 The Association for the Study of Animal Behaviour. Source

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