Pinniped diets inferred from scats: analysis of biases in prey occurrence

2003 ◽  
Vol 81 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Matías Arim ◽  
Daniel E Naya
Keyword(s):  
Empirical Studies ◽  
Assimilation Efficiency ◽  
Size Variation ◽  
Meal Size ◽  
Large Prey ◽  
Ecosystem Monitoring ◽  
Scat Analysis ◽  
Small Prey ◽  
Prey Mass ◽  
Resource Dynamics

The diets of pinnipeds have often been used to study their ecology and resource dynamics and in ecosystem monitoring. Scat analysis is now the most widely used method of inferring the diets of pinnipeds. Using a mathematical model the present study explores the expected biases in prey occurrence that are related to prey mass, proportion of loss of remains, predator assimilation efficiency, size of the scats collected, and meal size. With the exception of meal size, variation in parameters implied variation in the probability of biases in prey occurrence. Biases were asymmetric among prey sizes, but in contrast with previous ideas, the results indicate that small prey have smaller biases than large ones do. Furthermore, the number of scats required to detect a large prey was notably larger than that needed to detect a small prey with the same occurrence. The present study is not limited to a particular pinniped or prey species, so it has the potential to represent a general framework for interpreting the results of scat analysis in pinnipeds. The model complements empirical studies, advancing our comprehension of biases associated with prey occurrence in dietary studies of pinnipeds.

Alimentación de Coluber hippocrepis en el SE de la península Ibérica

1990 ◽  
Vol 11 (4) ◽  
pp. 325-337 ◽  
Author(s):  
Juan M. Pleguezuelos ◽  
Manuel Moreno
Keyword(s):  
Food Habits ◽  
Prey Type ◽  
Gut Contents ◽  
Ontogenetic Shift ◽  
The South ◽  
Extensive Area ◽  
Small Prey ◽  
Food Diversity ◽  
Prey Mass ◽  
Península Ibérica

AbstractThe food habits of 214 specimens of C. hippocrepis were analyzed throughout the year in an extensive area (44000 km2). This species mainly fed on vertebrates, especially mammals and reptiles which constituted more than 92% of its prey; other items included birds and invertebrates. Mammals represented more than 70% of the total prey mass. There was an ontogenetic shift in prey type; small snakes fed almost exclusively on small lizards, large snakes on rodents, although this change was gradual. There was not an ontogenetic shift in the percentage of snakes with gut contents, number of prey types or food diversity. C. hippocrepis captured relatively small prey. Most of them were taken head first, and those taken tail first were significantly smaller. We discuss the type of prey and the ontogenetic food shift in relation to the habits of this species in the south of Iberian Pcninsula.

scholarly journals Specific dynamic action, apparent assimilation efficiency, and digestive rate in an arboreal pitviper, Trimeresurus stejnegeri stejnegeri

2008 ◽  
Vol 86 (10) ◽  
pp. 1139-1151 ◽  
Author(s):  
Tein-Shun Tsai ◽  
How-Jing Lee ◽  
Ming-Chung Tu
Keyword(s):  
Assimilation Efficiency ◽  
Specific Dynamic Action ◽  
Meal Size ◽  
Digestive Physiology ◽  
Postprandial Metabolism ◽  
Preferred Temperature ◽  
Time To Peak ◽  
Dynamic Action ◽  
Effects Of Temperature ◽  
Arboreal Snakes

The major aims of this study were to assess the effects of temperature (15–35 °C) and meal size (less than 30% snake mass) on the metabolism and digestive physiology of Trimeresurus stejnegeri stejnegeri Schmidt, 1925 and to compare the results with those of terrestrial snakes. Specific dynamic action (SDA), peak Vo2, and scope of peak Vo2 increased with meal size. Temperature had little effect on SDA. With regression analysis, we found that baseline metabolic rates of T. s. stejnegeri were generally smaller than that for frequent feeders and larger than that for infrequent feeders. We generalized three types of SDA profiles among T. s. stejnegeri and terrestrial snakes (including frequent and infrequent feeders). Trimeresurus stejnegeri stejnegeri had a more shallow and extended profile of postprandial metabolism, which did not support our hypothesis that the pace of digestive metabolism of arboreal snakes is faster than that of terrestrial snakes. The apparent assimilation efficiency (range 0.698–0.884) was significantly lower at 15 °C. At the preferred temperature (26.5–28.8 °C) for a postprandial 50 g snake, the simulated ratios of four parameters (time to peak Vo2, first defecation time, gastric digestion time, and final defecation time) to SDA duration approximated 0.2, 0.5–0.7, 0.7, and 1.1, respectively.

The Inactivity of Animals: Influence of Stochasticity and Prey Size

Behaviour ◽  
1985 ◽  
Vol 92 (1-2) ◽  
pp. 1-8 ◽  
Author(s):  
Dorian Moss ◽  
William J. Sutherland
Keyword(s):  
Food Supply ◽  
Prey Capture ◽  
Prey Size ◽  
Large Prey ◽  
Small Prey ◽  
Sufficient Food

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.

Swimming ants and pitcher plants: a unique ant-plant interaction from Borneo

1995 ◽  
Vol 11 (4) ◽  
pp. 589-602 ◽  
Author(s):  
C. M. Clarke ◽  
R. L. Kitching
Keyword(s):  
Digestive System ◽  
Mosquito Larvae ◽  
Large Prey ◽  
Pitcher Plant ◽  
Small Prey ◽  
Plant Interaction ◽  
Nesting Sites ◽  
Mutualistic Association ◽  
The Relationship ◽  
Prey Items

ABSTRACTThe relationship between Camponotus sp. ants and the carnivorous pitcher plant, Nepenthes bicalcarata, from Borneo were investigated. The ants nest in the hollow tendrils of the plant, and feed on large prey items caught by the pitchers. These are hauled from the pitcher fluid by the ants and consumed. When large prey items are absent, the ants feed upon mosquito larvae which inhabit the pitcher fluid. The accumulation of excess prey in pitchers can lead to putrefaction of the contents, and disruption of the pitcher's digestive system. Experiments on the possible benefits of the ants' behaviour to the plant showed that the accumulation of excess prey and the putrefaction of the pitcher contents were significantly reduced in the presence of the ants. The accumulation of ammonia in pitchers was unaffected by the presence of the ants when small prey were added to pitchers, but was reduced significantly in the presence of ants when large prey were added. It is suggested that Camponotus sp. and N. bicalcarata have a mutualistic association, from which the ants obtain food and nesting sites and, in return, prevent damaging accumulation of excess prey in the pitchers.

Prey preference of a wasp determined by nest size supports the role of natural selection in body size evolution in Cassidinae leaf beetles

2021 ◽  
Author(s):  
Tadashi Shinohara ◽  
Yasuoki Takami
Keyword(s):  
Body Size ◽  
Natural Selection ◽  
Prey Species ◽  
Large Body ◽  
Size Variation ◽  
Prey Preference ◽  
Nest Size ◽  
Large Prey ◽  
Leaf Beetles ◽  
Body Sizes

Abstract The prey preference of a predator can impose natural selection on prey phenotypes, including body size. Despite evidence that large body size protects against predation in insects, the determinants of body size variation in Cassidinae leaf beetles are not well understood. We examined the prey preference of the digger wasp Cerceris albofasciata, a specialist predator of adult Cassidinae leaf beetles, and found evidence for natural selection on prey body size. The wasp hunted prey smaller than the size of their nest entrance. However, the wasp preferred larger prey species among those that could be carried into their nest. Thus, the benefits of large prey and the cost associated with nest expansion might determine the prey size preference. As expected from the prey species preference, the wasp preferred small individuals of the largest prey species, Thlaspida biramosa, and large individuals of the smallest prey species, Cassida piperata, resulting in natural selection on body sizes. In intermediate-sized prey species, however, there was no evidence for selection on body size. Natural selection on body size might explain the variation of prey morphologies that increase body size, such as explanate margins, in this group.

EFFECTS OF LOW RATES OF PREDATION ON SELECTED LIFE-HISTORY CHARACTERISTICS OF PODISUS MACULIVENTRIS (SAY) (HETEROPTERA: PENTATOMIDAE)

1990 ◽  
Vol 122 (2) ◽  
pp. 271-283 ◽  
Author(s):  
Robert N. Wiedenmann ◽  
Robert J. O’Neil
Keyword(s):  
Life History ◽  
Tenebrio Molitor ◽  
Green Bean ◽  
Large Prey ◽  
Podisus Maculiventris ◽  
Reproductive Patterns ◽  
Small Prey ◽  
Life History Characteristics ◽  
Heteroptera Pentatomidae ◽  
Survival Patterns

AbstractReproductive and survival patterns of the heteropteran predator Podisus maculiventris (Say) (Heteroptera: Pentatomidae) were measured under low prey inputs. A single prey, mealworm larva (Tenebrio molitor L.), of one of two sizes (120 or 30 mg), was given to predators for a 24-h period every 1, 2, 4, 8, or 16 days. Additional treatments included: predators provided prey in excess of attack rates; predators given no food; and predators given green bean slices only. Results showed that predators provided with prey survived regardless of feeding interval. When given large prey, predators showed reproductive patterns that were not clearly reflective of feeding interval; only predators fed at 8- and 16-day intervals showed reduced fecundity. When given small prey, the reproductive patterns of predators clearly reflected the feeding intervals. Predators that were fed less frequently laid fewer eggs, less often, and later in life.

Selection of Prey by Size in Ningaui Yvonneae

1996 ◽  
Vol 44 (3) ◽  
pp. 319 ◽  
Author(s):  
AP Woolnough ◽  
SM Carthew
Keyword(s):  
Energy Efficient ◽  
Prey Size ◽  
Handling Time ◽  
Optimal Foraging Theory ◽  
Large Prey ◽  
Small Prey ◽  
Upper Limit ◽  
The Relationship ◽  
Prey Items ◽  
Selection Of

The small dasyurid marsupial, Ningaui yvonneae, feeds opportunistically on invertebrates dominated by the orders Hymenoptera, Coleoptera and Araneae, but is capable of, and will, consume vertebrates such as skinks. When presented with a choice of prey N. yvonneae exhibited a strong preference for prey items on the basis of size. It consistently selected small prey items over large prey items. Small prey items represented the most energy-efficient prey option as the ningaui can more efficiently capture, subdue and consume them than it can larger prey. The relationship between prey size and handling time was exponential, indicating that there is an upper limit to the ability of N. yvonneae to process prey. Moreover, smaller cockroaches provided greater energy gain than larger ones, indicating that the costs of eating larger cockroaches energetically outweighed the energy return. These results are in agreement with optimal foraging theory.

Effects of prey size, meal size, meal composition, and daily frequency of feeding on the recovery of rodent remains from carnivore scats

1997 ◽  
Vol 75 (11) ◽  
pp. 1811-1817 ◽  
Author(s):  
Brian T. Kelly ◽  
Edward O. Garton
Keyword(s):  
Prey Size ◽  
Energy Content ◽  
Meal Size ◽  
Correction Factors ◽  
Physiological Mechanisms ◽  
Scat Analysis ◽  
Gastrointestinal Physiology ◽  
Daily Frequency ◽  
Feeding Trials ◽  
Meal Composition

Recovery of rodent bone and teeth from coyote (Canis latrans) scats (feces) varied with prey size, meal size, energy content of the meal, and the frequency with which prey were consumed. Mean percentages of mouse and rat teeth recovered ranged from 1% (SE = 0.5%, n = 5) to 24.4% (SE = 3.6%, n = 4) and from 13.8% (SE = 3.8%, n = 5) to 52.5% (SE = 16.6%, n = 5), respectively. A significant portion of this variation resulted from physiological mechanisms affecting how long prey were retained in the digestive acids of the stomach. Recovery of hair did not vary and thus it was considered to be nondigestible. Owing to the variation in the recovery of bone and teeth and the lack of variation in the recovery of hair, we recommend the use of teeth or bone to identify the small rodents present in carnivore scats, and then the use of a visual estimate of hair, or sample of hair, to apportion the scat to the prey items present. We caution against using the numbers of teeth or diagnostic bones to determine the number or amount of a prey item represented by a scat without addressing the variability in their recovery. The effects of gastrointestinal physiology should be considered when planning feeding trials to derive correction factors for scat analysis.

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