scholarly journals Flexibility in feeding behaviour may compensate for morphological constraints of fossoriality in the amphisbaenian Blanus cinereus

2013 ◽  
Vol 34 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Pilar López ◽  
Pilar López ◽  
José Martín ◽  
Pilar López ◽  
José Martín ◽  
...  

Morphological adaptations for burrowing, such as an elongated body, and a small head may constrain feeding behaviour in fossorial reptiles. We experimentally examined the effect of prey type on prey capture and handling behaviour of the amphisbaenian Blanus cinereus. This amphisbaenian showed four different handling modes according to the characteristics of each prey type. When prey diameter was narrower than gape-size, prey were consumed without prey processing; when prey diameter was wider than gape-size, B. cinereus shifted handling mode to prey processing. Amphisbaenians scraped or tore off bite-sized pieces of large prey and showed longer handling times for some prey types than most epigean saurians. Flexibility in feeding behaviour may allow amphisbaenians to exploit variable underground trophic resources, overcoming constraints of morphological adaptation to fossoriality.

2018 ◽  
Author(s):  
Alexander L. Davis ◽  
Matthew H. Babb ◽  
Brandon T. Lee ◽  
Christopher H. Martin

AbstractBotanical carnivory is a novel feeding strategy associated with numerous physiological and morphological adaptations. However, the benefits of these novel carnivorous traits are rarely tested. Here, we used field observations and lab experiments to test the prey capture function of the marginal spikes on snap traps of the Venus flytrap (Dionaea muscipula). Our field and laboratory results suggested surprisingly inefficient capture success: fewer than 1 in 4 prey encounters led to prey capture. Removing the marginal spikes decreased the rate of prey capture success for moderate-sized cricket prey by 90%, but this effect disappeared for larger prey. The nonlinear benefit of spikes suggests that they provide a better cage for capturing more abundant insects of moderate and small sizes, but may also provide a foothold for rare large prey to escape. Our observations support Darwin’s hypothesis that the marginal spikes form a ‘horrid prison’ that increases prey capture success for moderate-sized prey, but the decreasing benefit for larger prey is unexpected and previously undocumented. Thus, we find surprising complexity in the adaptive landscape for one of the most wonderful evolutionary innovations among all plants. These findings further enrich our understanding of the evolution and diversification of novel trap morphology in carnivorous plants.


2005 ◽  
Vol 83 (2) ◽  
pp. 268-273 ◽  
Author(s):  
Francisco Díaz-Fleischer

Optimal-foraging theory predicts how a predator would feed most efficiently when faced with a choice of two types of prey differing in profitability and density in the habitat. The predator should focus only on the more profitable prey, since any prey item eaten by the predator has a cost in terms of the time and resources taken to subdue and eat it. A study of the hunting behaviour and prey-type selection of the web-weaving spider Micrathena sagittata (Walckenaer, 1841) (Araneae: Araneidae) in the field is documented. In the first part of the study, prey of two sizes were offered in four sectors of the web (top, bottom, right, and left). A prey item was provided at one position of the web at a time. Attack time was recorded at each position. Also, choice and no-choice tests were carried out by offering prey in opposing web sectors (top and bottom) simultaneously. Large prey were more successfully captured in the upper parts than in the bottom parts of the web. In the choice test, spiders always preferred large prey to small prey, while in the no-choice test, spiders always responded to the first stimulus received. Two different attack strategies, depending on prey size, were observed. Hunting strategies and prey-size preference can be related to the cost of web construction and profitability of the prey type.


2001 ◽  
Vol 204 (21) ◽  
pp. 3621-3627 ◽  
Author(s):  
Anthony Herrel ◽  
Jay J. Meyers ◽  
Peter Aerts ◽  
Kiisa C. Nishikawa

SUMMARYChameleons capture prey items using a ballistic tongue projection mechanism that is unique among lizards. During prey capture, the tongue can be projected up to two full body lengths and may extend up to 600 % of its resting length. Being ambush predators, chameleons eat infrequently and take relatively large prey. The extreme tongue elongation (sixfold) and the need to be able to retract fairly heavy prey at any given distance from the mouth are likely to place constraints on the tongue retractor muscles. The data examined here show that in vivo retractor force production is almost constant for a wide range of projection distances. An examination of muscle physiology and of the ultrastructure of the tongue retractor muscle shows that this is the result (i) of active hyoid retraction, (ii) of large muscle filament overlap at maximal tongue extension and (iii) of the supercontractile properties of the tongue retractor muscles. We suggest that the chameleon tongue retractor muscles may have evolved supercontractile properties to enable a substantial force to be produced over a wide range of tongue projection distances. This enables chameleons successfully to retract even large prey from a variety of distances in their complex three-dimensional habitat.


1999 ◽  
Vol 77 (7) ◽  
pp. 1064-1074 ◽  
Author(s):  
Andrew N Iwaniuk ◽  
Sergio M Pellis ◽  
Ian Q Whishaw

We tested the validity of previously described relationships between forelimb structure and behaviour in mammals by measuring the forelimbs of 22 species of North American carnivores. Nine ratios were calculated from these measurements and made independent of the effects of allometry and phylogeny through the use of log-transformed regressions and independent contrasts analysis. The ratios were then directly compared with two behavioural traits: arboreal locomotion and vertebrate predation. Only five of the nine ratios exhibited a significant relationship with arboreal locomotion and three with vertebrate predation. It was concluded that the brachial index, relative size of the olecranon process, and total forelimb robusticity may be reliable predictors of arboreal locomotion, and that the brachial index, relative size of the olecranon process, and radial robusticity may be accurate predictors of vertebrate predation. The data also suggest that the morphology of the lower forelimb may be an important indicator of prey-capture and feeding behaviour in carnivores and could be used in conjunction with craniodental variables to extrapolate predatory behaviour of extinct species.


1985 ◽  
Vol 114 (1) ◽  
pp. 443-461 ◽  
Author(s):  
S. L. Tamm ◽  
A. G. Moss

High-speed cinematography of feeding Pleurobrachia revealed a stereo-typed sequence of ciliary motor responses underlying the feeding behaviour of this ctenophore. Prey capture by a tentacle first elicited high frequency beating in all comb rows, propelling the animal forward at a rapid speed for several seconds. This was followed by a brief period of inactivity on some or all comb rows. Then comb rows adjacent to the catching tentacle beat in the reverse direction, causing the ctenophore to spin rapidly toward this side and sweeping the prey-catching tentacle to the opened mouth, which bent towards it. After engulfing the prey, the animal slowly swam forward to re-set the relaxed tentacles as a fishing net. The patterns, timing, onset and coordination of these ciliary responses, particularly the unilateral reversal of comb rows on the catching side, are analysed with respect to possible conducting pathways mediating this behaviour.


1988 ◽  
Vol 66 (6) ◽  
pp. 1309-1317 ◽  
Author(s):  
John H. Larsen Jr. ◽  
John T. Beneski Jr.

Gape formation by the dusky salamander (Desmognathus) involves both upper and lower jaws and occurs in a manner similar to that of other terrestrial salamanders. As Desmognathus opens its mouth, ventral rotation of the mandibles is restricted but not stopped by the atlas–mandibular ligaments; the lower jaw is not propelled anteriorly. Tongue protraction, well beyond the mandibular symphysis, is always a major component of prey capture by this genus. After the sticky tongue pad has made contact with the prey, the salamander's head surges forward and the pad is rapidly retracted with the prey item attached. Aided by a unique suite of characters the mouth then snaps shut with considerable force. Our study supports the premise that Desmognathus is no different from most, if not all, terrestrial salamanders in its employment of tongue projection as a major feature in prey capture. We argue that the primary selective force for the unique configuration of desmognathine cephalic structures was enhancement of the ability of these small salamanders to capture relatively large prey without an increase in the size of the head and body.


2010 ◽  
Vol 278 (1709) ◽  
pp. 1209-1215 ◽  
Author(s):  
Jonathan N. Pruitt ◽  
Susan E. Riechert

How task specialization, individual task performance and within-group behavioural variation affects fitness is a longstanding and unresolved problem in our understanding of animal societies. In the temperate social spider, Anelosimus studiosus , colony members exhibit a behavioural polymorphism; females either exhibit an aggressive ‘asocial’ or docile ‘social’ phenotype. We assessed individual prey-capture success for both phenotypes, and the role of phenotypic composition on group-level prey-capture success for three prey size classes. We then estimated the effect of group phenotypic composition on fitness in a common garden, as inferred from individual egg-case masses. On average, asocial females were more successful than social females at capturing large prey, and colony-level prey-capture success was positively associated with the frequency of the asocial phenotype. Asocial colony members were also more likely to engage in prey-capture behaviour in group-foraging situations. Interestingly, our fitness estimates indicate females of both phenotypes experience increased fitness when occupying colonies containing unlike individuals. These results imply a reciprocal fitness benefit of within-colony behavioural variation, and perhaps division of labour in a spider society.


Behaviour ◽  
1985 ◽  
Vol 92 (1-2) ◽  
pp. 1-8 ◽  
Author(s):  
Dorian Moss ◽  
William J. Sutherland

As a consequence of prey capture being partly dependent upon chance, each individual may usually spend much of the day inactive even if the population is limited by its food supply. This applies particularly to species that eat large prey and thus experience considerable day-to-day variation in intake which restricts them to relatively rich habitats. Food will be found easily on most days and little time need be spent hunting although, occasionally, they will be unlucky and, despite searching all day, risk starvation. Predators of small prey can survive in environments that provide barely sufficient food as they experience little variation in intake: but they need to search all day to sustain themselves.


2019 ◽  
Author(s):  
Alejandro Damian-Serrano ◽  
Steven H.D. Haddock ◽  
Casey W. Dunn

AbstractPredator specialization has often been considered an evolutionary ‘dead-end’ due to the constraints associated with the evolution of morphological and functional optimizations throughout the organism. However, in some predators, these changes are localized in separate structures dedicated to prey capture. One of the most extreme cases of this modularity can be observed in siphonophores, a clade of pelagic colonial cnidarians that use tentilla (tentacle side branches armed with nematocysts) exclusively for prey capture. Here we study how siphonophore specialists and generalists evolve, and what morphological changes are associated with these transitions. To answer these questions, we: (1) measured 29 morphological characters of tentacles from 45 siphonophore species, (2) mapped these data to a phylogenetic tree, and (3) analyzed the evolutionary associations between morphological characters and prey type data from the literature. Instead of a dead-end, we found that siphonophore specialists can evolve into generalists, and that specialists on one prey type have directly evolved into specialists on other prey types. Our results show that siphonophore tentillum morphology has strong evolutionary associations with prey type, and suggest that shifts between prey types are linked to shifts in the morphology, mode of evolution, and genetic correlations of tentilla and their nematocysts. The evolutionary history of siphonophore specialization helps build a broader perspective on predatory niche diversification via morphological innovation and evolution. These findings contribute to understanding how specialization and morphological evolution have shaped present-day food webs.Significance StatementPredatory specialization is often associated with the evolution of modifications in the morphology of the prey capture apparatus. Specialization has been considered an evolutionary ‘dead-end’ due to the constraints associated with these morphological changes. However, in predators like siphonophores, armed with modular structures used exclusively for prey capture, this assumption is challenged. Our results show that siphonophores can evolve generalism and new prey-type specializations by modifying the morphological states, modes of evolution, and genetic correlations between the parts of their prey capture apparatus. These findings demonstrate how studying open-ocean non-bilaterian predators can reveal novel patterns and mechanisms in the evolution of specialization. Understanding these evolutionary processes is fundamental to the study of food-web structure and complexity.


2019 ◽  
Author(s):  
Edmund R. Hunt ◽  
Brian Mi ◽  
Rediet Geremew ◽  
Camila Fernandez ◽  
Brandyn M. Wong ◽  
...  

AbstractGroups of social predators capture large prey items collectively, and their social interaction patterns may impact how quickly they can respond to time-sensitive predation opportunities. We investigated whether various organizational levels of resting interactions (individual, sub-group, group), observed at different intervals leading up to a collective prey attack, impacted the predation speed of colonies of the social spider Stegodyphus dumicola. We found that in adult spiders overall group connectivity (average degree) increased group attack speed. However, this effect was detected only immediately before the predation event; connectivity two and four days before prey capture had little impact on the collective dynamics. Significantly, lower social proximity of the group’s boldest individual to other group members (closeness centrality) immediately prior and two days before prey capture was associated with faster attack speeds. These results suggest that for adult spiders, the long-lasting effects of the boldest individual on the group’s attack dynamics are mediated by its role in the social network, and not only by its boldness. This suggests that behavioural traits and social network relationships should be considered together when defining keystone individuals in some contexts. By contrast, for subadult spiders, while the group maximum boldness was negatively correlated with latency to attack, no significant resting network predictors of latency to attack were found. Thus, separate behavioural mechanisms might play distinctive roles in determining collective outcomes at different developmental stages, timescales, and levels of social organization.Significance statementCertain animals in a group, such as leaders, may have a more important role than other group members in determining their collective behavior. Often these individuals are defined by their behavioral attributes, for example, being bolder than others. We show that in social spiders both the behavioral traits of the influential individual, and its interactions with other group members, shape its role in affecting how quickly the group collectively attacks prey.


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