First Recorded Account of a White Shark Agonistic Pectoral Fin Depression Behavior at Guadalupe Island, Mexico

An agonistic display by a white shark was observed and photographed during a cage dive at Guadalupe Island in November 2015. Exhibiting exaggerated pectoral fin depression, agonistic behaviors have been previously observed and described in several shark species. This account may be the first record of a white shark in close proximity to a caged diver, exhibiting strong pectoral fin depression significantly dipped, in the mid-agonistic display. Such displays should be considered as aggressive and potentially life-threatening by those using the ocean for recreational or professional purposes.

Effect of losing a fight on later agonistic behavior toward unfamiliar conspecifics in male Syrian hamsters

In many species, agonistic interactions result in social relationships that are stable over time. In Syrian hamsters, two unfamiliar males that are placed together will fight vigorously and a clear winner/loser relationship is usually established. In subsequent interactions, the loser will flee soon after detecting the familiar winner. Here we tested the hypothesis that losing a fight with a conspecific will affect future agonistic interactions not only toward that individual （i.e., the familiar winner） but also toward unfamiliar conspecifics. To test this hypothesis we paired two Syrian hamster males in three trials on one day in which the loser had tile opportunity to escape the winner. The next day the loser was paired with an unfarniliar male, also for three trials. If he lost again, he was tested on a third day with a third unfamiliar male. Subjects were those males that were losers on all three days. The latency to escape on the first trial on Days 2 and 3 was significantly shorter than on the first trial on Day l, indicating that losing against the first male affected the response toward unfamiliar males. However, the latency to escape on the first trial on Days 2 and 3 was significantly longer than that on the third trial on the preceding day, indicating that a loser treats unfamiliar males differently than a familiar winner. These results suggest that a defeat during an interaction with one male affects later agonistic behavior towards other, unfamiliar males [Current Zoology 57 （4）： 449-452, 2011].

Galls as a Disputed Resource for Female Parasitoid Wasps Contests

We investigated how the parasitoid Torymus sp. (Hymenoptera: Torymidae) attacking galls of Schismatodiplosis lantanae (Diptera: Cecidomyiidae) on Lantana camara (Verbenaceae) behaves in the presence of a conspecific female competitor in the patch. Presence of a competitor greatly changed resident exploitation behavior. Wasps alone spent more time in gall exploitation behaviors (walk-antennate and probe) and in post-oviposition behaviors (stationary and groom), and when intruders were present they spent more time walking. The attack strategy was through threatening: raising wings and pointing the antennae towards the opponent. Different from theoretical expectations, residents were not always the attacker. Number of galls in the patch and female wasp size did not affect contest outcomes, although gall exploitation time and time on leaf were significant factors for the probability of having attacks. Overall, the study highlights the fact that intruder interest in the host was the main cause of contests and also this is a unique report both in terms of the target species and the nature of the disputed resource, a gall-inducer inside a singular spatial unit, the gall.

Controlling the decision to fight or flee： the roles of biogenic amines and nitric oxide in the cricket

Aggression is a common behavioral strategy employed by animals to secure limited resources, but must be applied with restraint to limit potential costs including injury. How animals make the adap- tive decision to fight or flee is barely known. Here, we review our work on crickets that reveals the roles of biogenic amines, primarily octopamine （the insect analog of noradrenaline） and nitric oxide （NO）. Using aminergic drugs, we found that amines are not essential for actually initiating aggres- sion. However, octopamine is necessary for mediating the aggression-promoting effects of poten- tially rewarding experiences including stimulation with a male antenna, physical exertion, winning, and resource possession. Hence, octopamine can be considered as the motivational component of aggression. Imposed handicaps that impede aggressive signaling revealed that the agonistic actions of an opponent perceived during fighting act to reduce aggression, and that crickets make the deci- sion to flee the moment the accumulated sum of such aversive experiences exceeds some critical level. Treatment with nitridergic drugs revealed that the impact of the opponent＇s aggressive actions is mediated by NO. NO acts to suppress aggression by promoting the tendency to flee and is primarily responsible for the depressed aggressiveness of subordinates after social defeat. Octopamine and dopamine can each restore aggression in subordinates, but only dopamine is necessary for normal recovery. The role of serotonin remains unclear, and is discussed. We conclude that octopamine and NO control the decision to fight or flee by mediating the effects of potentially rewarding and aversive experiences, respectively.