Size-dependent predation risk partly explains the sex-related marking polymorphism in the sexually size-dimorphic pygmy grasshopperTetrix japonica

2012 ◽  
Vol 16 (2) ◽  
pp. 136-144 ◽  
Author(s):  
Kaori Tsurui ◽  
Atsushi Honma ◽  
Takayoshi Nishida
Keyword(s):  
Predation Risk ◽  
Size Dependent

Perceived predation risk, parasitism, and the foraging behavior of a freshwater snail (Potamopyrgus antipodarum)

1998 ◽  
Vol 76 (10) ◽  
pp. 1878-1884 ◽  
Author(s):  
Edward P Levri
Keyword(s):  
Predation Risk ◽  
Foraging Behavior ◽  
Freshwater Snail ◽  
Potamopyrgus Antipodarum ◽  
Plain Water ◽  
Fish Diet ◽  
Fish Predator ◽  
Size Dependent ◽  
Individual Size ◽  
Perceived Predation Risk

Foraging behavior can be influenced by such factors as predation risk, individual size, and parasite infection. Snails (Potamopyrgus antipodarum) placed in tanks with large rocks were exposed to four types of water: (1) water with crushed snails, (2) water from a tank in which fish (Gobiomorphus cotidianus) were fed only trout chow, (3) water from a tank where the fish were also fed snails, and (4) plain water. Snails could respond by moving to the top of rocks (where algal food was present) or to the bottom of rocks (where the predation risk was lower). The snails responded to fish chemicals by moving to the bottom of rocks. The response was dependent on snail size and fish diet. Smaller snails moved to the bottom of rocks more than larger snails did. Trematode-infected snails were found on top of the rocks more than other classes of snails, but infected snails still moved to the bottom of rocks in response to the fish predator. Snails eaten by fish in the field tend to be smaller than snails in the overall available population. Thus, snails that are more vulnerable to predation respond more intensely to the odor of fish by moving to the bottom of rocks. This size-dependent response to fish appears to be independent of the occurrence of trematode infection.

Size-dependent resource limitation and foraging-predation risk trade-offs: growth and habitat use in young arctic char

Oikos ◽  
2004 ◽  
Vol 104 (1) ◽  
pp. 109-121 ◽  
Author(s):  
Pär Byström ◽  
Jens Andersson ◽  
Lennart Persson ◽  
André M. De Roos
Keyword(s):  
Habitat Use ◽  
Predation Risk ◽  
Resource Limitation ◽  
Arctic Char ◽  
Size Dependent ◽  
Trade Offs

Size-dependent foraging behaviour and use of cover in juvenile coho salmon under predation risk

1997 ◽  
Vol 75 (10) ◽  
pp. 1642-1651 ◽  
Author(s):  
Ulrich G. Reinhardt ◽  
Michael C. Healey
Keyword(s):  
Predation Risk ◽  
Coho Salmon ◽  
Natural Environments ◽  
Foraging Habitat ◽  
Risk Avoidance ◽  
Control Groups ◽  
Average Growth ◽  
Predation Threat ◽  
Size Dependent ◽  
The Difference

Foraging and use of cover by juvenile coho salmon (Oncorhynchus kisutch) were affected by predation threat in both seminatural channels and laboratory streams. In the field, coho salmon preferred stream sections with brushy cover only when under threat from hunting common mergansers. The mergansers had their highest capture success in pools without cover. Predation threat also caused coho salmon to use cover more as foraging habitat and to aggregate more in favourable positions at the head of the pool. In the laboratory, under simulated predation threat, fish using a refuge were significantly larger than those in the risky habitat. This pattern persisted for 2 days after the predation threat was discontinued. The average growth of coho salmon under predation threat was depressed and the difference in growth between large and small individuals was less than in control groups. We argue that larger fish were more averse to predation risk than smaller fish and that the smaller fish took advantage of feeding opportunities indirectly provided as a result of the predation risk. We speculate that in natural environments, predation may depress growth rates because of risk-avoidance behaviour but may also serve to reduce growth-rate differences among size classes within a cohort.

Size-related changes in diel distribution of young grayling (Thymallus thymallus)

1995 ◽  
Vol 52 (9) ◽  
pp. 1842-1848 ◽  
Author(s):  
P. Sempeski ◽  
P. Gaudin
Keyword(s):  
Energy Conservation ◽  
Predation Risk ◽  
Distribution Patterns ◽  
Main Channel ◽  
River Channel ◽  
Habitat Shift ◽  
Precise Description ◽  
Thymallus Thymallus ◽  
Size Dependent ◽  
Marginal Habitats

An approach based on direct observation from the riverbank allowed a precise description of the size-dependent distribution patterns of young grayling. The smallest larvae (15–20 mm) were mainly observed in the upper layers of the water column and very close to the riverbank. With increasing age and size (20–35 mm), old larvae and young parr began to hold positions closer to the bottom and to the edge of the main channel. From a size of 35–40 mm. an increasing number of juveniles were observed in the river channel, holding a benthic position. A diel habitat shift was also shown for individuals of all stages, between their respective daytime habitats and dead zones, where they were observed resting on the bottom in very shallow water at night. The benefits of this shift might be expressed in terms of energy conservation and (or) decreased predation risk. This study points out the importance of marginal habitats in the first weeks of grayling life as (i) exclusive nursery areas for larvae that use them both by day and by night and (ii) resting habitats for juveniles at night.

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