Search results for "alistus"
showing 10 items of 84 documents
Balancing food, activity and the dangers of sunlit nights
2019
Living in northern latitudes poses challenges to the animals that live in those habitats. The harsh environment provides a short breeding season where the sunlit summer nights provide little reprieve from visibility to predators and increased risk. In this paper, we tested the activity and food choice patterns of bank voles Myodes glareolus in early spring season, categorized by 18 h of daylight and 6 h of dusk in every day cycle. We found that territorial females showed a less predictable pattern of activity than males that were most active during the hours of dusk. The voles also showed preference to forage on high carbohydrate foods at sunset, while switching over to a more protein and f…
Lämpötilan vaikutus täpläravun (Pacifastacus leniusculus Dana) kasvuun sekä ravintotiheyden vaikutus täpläravun ja jokiravun (Astacus astacus L.) rav…
2016
Alun perin pohjoisamerikkalaisen täpläravun (Pacifastacus leniusculus Dana) levinneisyys on 1960-luvulta lähtien laajentunut kattamaan Etelä- ja Keski-Suomessa laajoja vesialueita, jotka ovat aiemmin olleet jokiravun (Astacus astacus L.) elinaluetta. Täpläravun mahdollisesti jokiravusta eroavaa ravinnonkulutusta ja saalislajeihin kohdistamaa saalistusta on pyritty arvioimaan täpläravulle kehitetyllä bioenergeettisellä mallilla, jonka jatkokehitystä ja toimivuuden arviointia tämä tutkimus tukee. Täpläravun kasvua selvitettiin 30 vrk:n ajan kolmessa Suomen luonnonoloja vastaavassa lämpötilassa, 10, 16 ja 22 °C:ssa. Ravintotiheyden vaikutusta täpläravun ja jokiravun mahdollisesti aktiiviseen k…
Lake size and fish diversity determine resource use and trophic position of a top predator in high-latitude lakes
2015
Prey preference of top predators and energy flow across habitat boundaries are of fundamental importance for structure and function of aquatic and terrestrial ecosystems, as they may have strong effects on production, species diversity, and food-web stability. In lakes, littoral and pelagic food-web compartments are typically coupled and controlled by generalist fish top predators. However, the extent and determinants of such coupling remains a topical area of ecological research and is largely unknown in oligotrophic high-latitude lakes. We analyzed food-web structure and resource use by a generalist top predator, the Arctic charr Salvelinus alpinus (L.), in 17 oligotrophic subarctic lakes…
Olfactory cues and the value of information : Voles interpret cues differently based on recent predator encounters
2018
Prey strategically respond to the risk of predation by varying their behavior while balancing the tradeoffs of food and safety. We present here an experiment that tests the way the same indirect cues of predation risk are interpreted by bank voles, Myodes glareolus, as the game changes through exposure to a caged weasel. Using optimal patch use, we asked wild-caught voles to rank the risk they perceived. We measured their response to olfactory cues in the form of weasel bedding, a sham control in the form of rabbit bedding, and an odor-free control. We repeated the interviews in a chronological order to test the change in response, i.e., the changes in the value of the information. We found…
The evolution and ecology of multiple antipredator defences
2023
Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of speci…
Trophic ecology of piscivorous Arctic charr (Salvelinus alpinus (L.)) in subarctic lakes with contrasting food-web structures
2019
The trophic ecology of piscivorous Arctic charr (Salvelinus alpinus (L.); charr) in the food webs of large subarctic lakes is not well understood. We assessed charr diets, parasites, growth, maturity, and stable isotope ratios in Fennoscandian subarctic lakes dominated by monomorphic or polymorphic whitefish (Coregonus lavaretus (L.)) populations. Charr density was low in all lakes, except in profundal habitats. Charr shifted to piscivory at small size (16–25 cm total length) and consumed a range of prey-fish sizes (2–25 cm). Cannibalism was observed in a few individuals from one monomorphic whitefish lake. Charr matured at 37–51 cm (5–8 years old), grew to 52–74 cm maximum observed length …
Warning signalling in European vipers and their mimics : implications for conservation of the smooth snake
2014
Epävakaa mimeettinen halu Robert Walserin romaanissa Konttoristi
2019
Artikkelissa tutkitaan sveitsiläisen kirjailijan Robert Walserin romaania Konttoristi René Girardin esittämän mimeettisen halun teorian, kaunasta virittyvän syntipukkimekanismin ja myös niistä erillisen mimetismin näkökulmista. Girardin teoriaan luodun katsauksen jälkeen eritellään konttoristina työskentelevän päähenkilön asemaa taloudellisen ja sosiaalisen kilpailun piirissä. Toisin kuin Girardin omissa analyyseissa, päähenkilö on pikemmin mimeettisen halun epävarma ja välillä vastahankainen tukija ja kosketuspinta kuin sen vallassa oleva toimija. Lisäksi käsitellään Walserin kertomatavan vaikutuksia sekä tarinan että kilpailevasta jäljittelystä poikkeavien imaginaaristen vastaavuuksien ta…
Vapaus valita? Nuorten pirstaloituva liikuntakulttuuri
2017
Keskustelu lasten ja nuorten liikkumisesta on muodostunut liikuntakulttuuripohdintojen kestoaiheeksi. Yhtäältä on huolestuttu varttuvan sukupolven liian vähäisestä – jopa terveyttä uhkaavasta – fyysisestä aktiivisuudesta. Toisaalta uusimmat sosialisaatiotulkinnat korostavat nuorison omia ruumiillisuuden valintoja. Tällöin perinteinen aikuisjohtoinen urheilukulttuuri on saanut rinnalleen monia nuorisokulttuurisen liikkumisen muotoja. nonPeerReviewed