As marine ecosystems are harvested or modified by anthropogenic or natural factors, there is an i... more As marine ecosystems are harvested or modified by anthropogenic or natural factors, there is an increasing demand for indicators of trophic web health or status. The Magellanic Penguin (Spheniscus magellanicus) is a widely distributed species that forages in the Patagonian Shelf. During breeding, this species is a central-place forager that feeds mainly on schooling fish, with Argentine anchovy (Engraulis anchoita) being the dominant prey in the north and Fuegian sprat (Sprattus fuegensis) in the south of the Argentine Patagonian distribution (40–55°S). Like most forage fish, both prey species display large natural interannual recruitment fluctuations. We used stable isotope analysis of adult Magellanic penguin blood obtained at twelve colonies along its Patagonian latitudinal range to assess changes in isotopic niche and in trophic level as a response to interannual changes in abundance and spatial segregation of forage fish size classes, respectively. Magellanic penguins showed la...
A specific study has been carried out for the first time to investigate the homing capability and... more A specific study has been carried out for the first time to investigate the homing capability and daily home range of the spiny lobster Palinurus elephas by means of ultrasonic telemetry. Nine lobsters collected in the Capo Gallo — Isola delle Femmine marine protected area (northwestern Sicily, central Mediterranean) were tagged with miniaturized transmitters and released at a single site inside the protected area. The lobsters were monitored with the purpose of calculating their horizontal and vertical positions, analysing their movement patterns to assess their homing capability, and calculating their daily home range. Five lobsters moved back close to the capture sites within the first 20 hours after release (‘homed’). The remaining four lobsters ‘relocated’ to a different refuge. Homed lobsters had a larger home range than relocated lobsters. This study provides the first description of a homing pattern with high spatial resolution in the wild European spiny lobster as inferred by ultrasonic telemetry.
Thermoregulation could represent a significant fraction of the total energy budget of endotherms ... more Thermoregulation could represent a significant fraction of the total energy budget of endotherms under unfavourable environmental conditions. This cost affects several traits of the ecology of an organism such as its behaviour, distribution, or life history. Heat produced by muscle contraction during activity can be used to pay for heat loss or thermoregulation in many species (known as “thermal substitution”). This study seeks to unite the effects of temperature, depth, and activity on the energetic costs of endotherm divers using the Magellanic penguin as model species and to evaluate whether penguins may benefit from thermal substitution. This species operates under highly variable temperature and depth conditions along its breeding range and provides an ideal natural experiment. A developed thermodynamic model describing foraging activity predicted that the major element affecting heat loss was depth, exacerbated by temperature. Birds living in colder waters are predicted to be able to minimize costs by executing shallower dives and benefit from thermal substitution by swimming faster, particularly during deeper dives. The model was evaluated in two contrasting scenarios: (1) when birds swim near the surface commuting to the foraging areas and (2) when birds dive to depth to forage. Activity data from tags on free-living penguins indicated two of these predictions were apparent; penguins generally travelled faster while commuting at the surface in colder waters, while birds from warmer water colonies dived deeper while foraging. Contrary to predictions, however, penguins swam slower at deeper depths during both descent and ascent phases of foraging dives. These results suggest that penguins may benefit from thermal substitution by swimming faster when birds perform shallow dives commuting to and back from foraging areas, but they provide no evidence of behavioural response (via swimming faster) for thermoregulation when diving to depth to forage. Reasons for this are discussed and include the relevance of prey abundance in 3-d space and maximizing dive duration by conserving oxygen reserves. The way the bird operates will have profound consequences for the energy needed and therefore necessary energy acquisition rates. Expansion of our findings to other diving endotherms might help explain both global activity patterns and energy flow in ecosystems.
As marine ecosystems are harvested or modified by anthropogenic or natural factors, there is an i... more As marine ecosystems are harvested or modified by anthropogenic or natural factors, there is an increasing demand for indicators of trophic web health or status. The Magellanic Penguin (Spheniscus magellanicus) is a widely distributed species that forages in the Patagonian Shelf. During breeding, this species is a central-place forager that feeds mainly on schooling fish, with Argentine anchovy (Engraulis anchoita) being the dominant prey in the north and Fuegian sprat (Sprattus fuegensis) in the south of the Argentine Patagonian distribution (40–55°S). Like most forage fish, both prey species display large natural interannual recruitment fluctuations. We used stable isotope analysis of adult Magellanic penguin blood obtained at twelve colonies along its Patagonian latitudinal range to assess changes in isotopic niche and in trophic level as a response to interannual changes in abundance and spatial segregation of forage fish size classes, respectively. Magellanic penguins showed la...
A specific study has been carried out for the first time to investigate the homing capability and... more A specific study has been carried out for the first time to investigate the homing capability and daily home range of the spiny lobster Palinurus elephas by means of ultrasonic telemetry. Nine lobsters collected in the Capo Gallo — Isola delle Femmine marine protected area (northwestern Sicily, central Mediterranean) were tagged with miniaturized transmitters and released at a single site inside the protected area. The lobsters were monitored with the purpose of calculating their horizontal and vertical positions, analysing their movement patterns to assess their homing capability, and calculating their daily home range. Five lobsters moved back close to the capture sites within the first 20 hours after release (‘homed’). The remaining four lobsters ‘relocated’ to a different refuge. Homed lobsters had a larger home range than relocated lobsters. This study provides the first description of a homing pattern with high spatial resolution in the wild European spiny lobster as inferred by ultrasonic telemetry.
Thermoregulation could represent a significant fraction of the total energy budget of endotherms ... more Thermoregulation could represent a significant fraction of the total energy budget of endotherms under unfavourable environmental conditions. This cost affects several traits of the ecology of an organism such as its behaviour, distribution, or life history. Heat produced by muscle contraction during activity can be used to pay for heat loss or thermoregulation in many species (known as “thermal substitution”). This study seeks to unite the effects of temperature, depth, and activity on the energetic costs of endotherm divers using the Magellanic penguin as model species and to evaluate whether penguins may benefit from thermal substitution. This species operates under highly variable temperature and depth conditions along its breeding range and provides an ideal natural experiment. A developed thermodynamic model describing foraging activity predicted that the major element affecting heat loss was depth, exacerbated by temperature. Birds living in colder waters are predicted to be able to minimize costs by executing shallower dives and benefit from thermal substitution by swimming faster, particularly during deeper dives. The model was evaluated in two contrasting scenarios: (1) when birds swim near the surface commuting to the foraging areas and (2) when birds dive to depth to forage. Activity data from tags on free-living penguins indicated two of these predictions were apparent; penguins generally travelled faster while commuting at the surface in colder waters, while birds from warmer water colonies dived deeper while foraging. Contrary to predictions, however, penguins swam slower at deeper depths during both descent and ascent phases of foraging dives. These results suggest that penguins may benefit from thermal substitution by swimming faster when birds perform shallow dives commuting to and back from foraging areas, but they provide no evidence of behavioural response (via swimming faster) for thermoregulation when diving to depth to forage. Reasons for this are discussed and include the relevance of prey abundance in 3-d space and maximizing dive duration by conserving oxygen reserves. The way the bird operates will have profound consequences for the energy needed and therefore necessary energy acquisition rates. Expansion of our findings to other diving endotherms might help explain both global activity patterns and energy flow in ecosystems.
Uploads
Papers by Javier Ciancio