Biology subjects

Pessoa, D. M. A.

Publications and source records attributed to Pessoa, D. M. A..

4 recordsLinked to original sources

bioRxiv2021

Detection of conspicuous and cryptic food by marmosets (Callithrix jacchus): An evaluation of the importance of color and shape cues

Since 19th century, the adaptive function of color vision for object identification has fascinated science. Countless articles uncovered the advantages of trichromacy (i.e., color vision expressed by most humans) in detecting yellowish/reddish targets against a background of mature green leaves. Unfortunately, the same attention was not offered to achromatic visual information, that had their physiological foundations much more explored than their possible adaptive function. So far, mostly because of studies conducted in humans, we know that achromatic cues might also play an important role in object identification, particularly when camouflage is involved. For instance, dichromacy (i.e., color vision expressed by many colorblind humans), favors the detection of camouflaged targets by exploitation of shape cues. The present study sought to evaluate the relative importance of color and shape cues on the detection of food targets by female and male marmosets (Callithrix jacchus). Animals were observed with respect to their foraging behavior and the number of food targets captured. We confirmed that females are advantageous in detecting conspicuous food against a green background and revealed that females and males rely on shape cues to segregate cryptic food. Unexpectedly, males outperformed females in cryptic food foraging. Camouflage improved males (but not females) performance. HighlightsO_LIShape cues alone improve capture of cryptic targets by female and male marmosets. C_LIO_LIThe sole use of color cues leads to clear-cut foraging performances between sex. C_LIO_LIFemales outperform males when searching for orange food against a green background. C_LIO_LIMales outperform females when searching for green food against a green background. C_LIO_LIMales match females performance when searching for orange camouflaged food. C_LI

animal behavior and cognition↗

bioRxiv2021

The trade-off between color and size in lizards' conspicuous tails

A tail of conspicuous coloration is hypothesized to be an advantageous trait for many species of lizards. Predator attacks would be directed to a non-vital, and autotomizable, body part, increasing the chance of survival. However, as body size increases it also increases the signaling area that could attract predators from greater distances, increasing the overall chance of predation. Here, we test the hypothesis that there is a trade-off between tail color and size, affecting predation probabilities. We used plasticine replicas of lizards to study the predation patterns of small and large lizards with red and blue tails. In a natural environment, we exposed six hundred replicas subjected to the attack of free-ranging predators. Large red-tailed models were attacked more quickly, and more intensely, by birds. Mammals and unidentified predators showed no preference for any size or colors. The attacks were not primarily directed to conspicuous tails when compared to the body or the head of our replicas. Our study suggests that red color signals in large lizards could enhance their detection by visually oriented predators (i.e., birds). The efficacy of conspicuous tails as a decoy may rely on associated behavioral displays, which are hard to test with static replicas. HighlightsO_LIThe roles of blue and red tails as decoys were not corroborated. C_LIO_LITail color and size interact while influencing predation rates. C_LIO_LILarger red-tailed lizards are more prone to be attacked by birds. C_LIO_LIThe benefit of having conspicuous tails appears to decrease as body size increases. C_LI

animal behavior and cognition↗

bioRxiv2021

The role of claw colouration in fiddler crabs' mate choice: Private communication channel or handicap?

Colour cues play an important role in sexual selection and conspecific recognition. Literature shows that conspecifics might enjoy their everyday chat, without ever worrying about occasional eavesdroppers (e.g., predators), when information interchange evolves into a private communication channel. Yet, when signalling is converted into foraging cues by predators, their prey must pay the due cost for sustaining conversation. For that matter, fiddler crabs draw attention for having flashy enlarged claws that could potentially attract the attention of many predators. Surprisingly, the costs associated with claw colouration in fiddler crabs are still poorly understood and have never been studied in American species. Here, we initially examine whether hypertrophied claws of American thin-fingered fiddler crabs (Leptuca leptodactyla) reflect UV-light and how conspecific females react to these cues. Then we test two alternative hypotheses concerning the role of claw colouration in fiddler crabs mate choice: a) that claw colouration evolved into a private communication channel, which could have significantly lowered signalling costs for males; b) that claw colouration is conspicuous to potential reproductive partners, as well as to predators, making colour signalling by males very costly (i.e., a handicap). Thereafter, we measured the reflectance spectra from several enlarged claws and modelled their chromatic contrast against the background spectrum, considering the visual systems of conspecific fiddler crabs and two kinds of predators (terns and plovers). We also tested female conspecifics preference towards enlarged claws that reflected UV-light or other colour cues, by artificially altering claw colouration. Our results show a clear female preference for UV reflecting males. We also found that natural enlarged claws should be highly detectable by avian predators, refuting the private communication channel hypothesis. Furthermore, since female fiddler crabs select the most flamboyant claws from the sandy background, claw colouration in fiddler crabs can be understood as an honest signal. HIGHLIGHTSO_LIThe hypertrophied claws of male Leptuca leptodactyla reflect UV light. C_LIO_LIFemale fiddler crabs display a natural preference for UV light cues. C_LIO_LIConspicuous claws function as handicaps and may honestly signal individual quality. C_LIO_LIMale enlarged claws are more conspicuous to birds than to crabs. C_LIO_LIOur data refute the presence of a private communication channel in L. leptodactyla. C_LI

animal behavior and cognition↗

bioRxiv2020

Influence of color and brightness on ontogenetic shelter preference by prawns (Macrobrachium rosenbergii)

The giant river prawn (Macrobrachium rosenbergii), native to rivers and river mouths of different Asian countries, is a heavily widespread species that has been introduced around the world due to its great commercial importance. These prawns are farmed under many different conditions that might translate to a great range of light environments, which impact their behavior and productivity. Here, as a contribution for prawns welfare and economical productivity, we present the first study employing both visual modeling and behavioral data to evaluate ontogenetic changes on color preference of juveniles and adults of M. rosenbergii. For this purpose, we offered ten shelters of different colors to juveniles and adults and registered their preference. Our results showed that the criterion for shelter preference changed with ontogeny, since juveniles chose shelters based on chromaticity (preference for blue), while adults based their decisions on brightness (preference for dark gray). This preference of adults for dark colors is probably associated with a light avoidance behavior. We recommend providing blue shelters for juveniles and dark shelters for adults.

animal behavior and cognition↗