12/9/2023 0 Comments Ambush predators vsHowever, a switch in activity and foraging behaviour to maintain prey consumption does not necessarily imply maintained predator growth and fitness, as higher activity costs might not be balanced by the energy gain, and thus be less efficient 6. Predators able to shift their foraging strategies may be able to maintain the total number of prey captures as the yield of their favoured foraging strategy is reduced 10, 11, 12. This ability is species-specific and it has been documented in various groups of invertebrates 6, 12 and fish 9, 11, where it has implications for hunting success. Some predators can alter their foraging behaviour and activity by switching between ambush and active pursuit 9, 10, 11, 12 depending on the presence/absence of macrophytes. 5, 6, 7) via affecting predator–prey detection, encounter and catchability 8. Macrophytes can substantially alter the behaviour of both prey and predators (e.g. Submerged macrophytes are among the main structuring components in freshwater ecosystems. Physical structures, either biotic or abiotic, may also provide suitable substrate for primary producers, filtering organisms etc., and thus increase the food availability for predators 5. The presence of varied structures increases environmental heterogeneity and the range of available potential habitats 4, and by providing shelter for prey or cover for predators structures have a crucial role in predator–prey interactions 5. Much focus has been given to the role that habitat complexity plays in structuring and functioning at the population level, both in aquatic and terrestrial ecosystems 1, 2, 3. The composition of biotic assemblages is heavily influenced by habitat heterogeneity arising from both abiotic and biotic components. Our study demonstrated how differences in structural complexity mediated prominent changes in the foraging behaviour of an apex predator, which in turn may have effects on the prey community. It could lead to increased prey encounter and cause better growth in the LSC lake. We concluded that pike in the HSC lake displayed a behaviour consistent with a prevalent ambush predation behaviour, whereas the higher activity and larger space use in the LSC lake indicated a transition to more active search behaviour. Despite observed differences between lakes, stable isotopes analyses indicated a high dependency on littoral food sources in both lakes. Pike displayed increased activity, space use, individual growth as well as behavioural differentiation and spent more time in open waters in the LSC lake. Behaviour of pike was studied with whole-lake acoustic telemetry tracking, supplemented by stable isotope analysis of pike prey utilization and survey fishing data on the prey fish community. We tested whether contrasting structural complexity in two newly colonised lakes (low structural complexity lake-LSC high structural complexity-HSC) was associated with contrasting behaviour in an aquatic apex predator, Northern pike ( Esox lucius hereafter pike) present in the lakes. Structural complexity is known to influence prey behaviour, mortality and population structure, but the effects on predators have received less attention.
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