Browsing by Author "Jorge, Paulo"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
- Asymmetrical processing of olfactory input in the piriform cortex mediates "activation" of the avian navigation circuitryPublication . Jorge, Paulo; Marques, Paulo A. M.; Pinto, Belmiro V.; Phillips, John B.The role of odors in the long-distance navigation of birds has elicited intense debate for more than half a century. Failure to resolve many of the issues fueling this debate is due at least in part to the absence of controls for a variety of non-specific effects that odors have on the navigational process. The present experiments were carried out to investigate whether the olfactory inputs are involved only in “activation” of neuronal circuitry involved in navigation or are also playing a role in providing directional information. Experienced adult pigeons were exposed to controlled olfactory stimuli during different segments of the journey (release site vs. displacement + release site). Protein levels of IEGs (immediate early genes used to mark synaptic activity) were analyzed in areas within the olfactory/navigation avian circuitry. The results indicate that 1) exposure to natural odors at the release site (and not before) elicit greater activation across brain regions than exposure to filtered air, artificial odors, and natural odors along the entire outward journey (from home to the release site, inclusive); 2) activation of the piriform cortex in terms of odor discrimination is lateralized; 3) activation of the navigation circuitry is achieved by means of lateralized activation of piriform cortex neurons. Altogether, the findings provide the first direct evidence that activation of the avian navigation circuitry is mediated by asymmetrical processing of olfactory input occurring in the right piriform cortex.
- Decision-making in pigeon flocks: A democratic view of leadershipPublication . Jorge, Paulo; Marques, Paulo A. M.When travelling in groups, animals frequently have to make decisions on the direction of travel. These decisions can be based on consensus, when all individuals take part in the decision (i.e. democratic decision; social information), or leadership, when one member or a minority of members make the decision (i.e. despotic decision; personal information). Here we investigated whether decision-making on the navigation of small flocks is based on democratic or despotic decisions. Using individual and flock releases as the experimental approach, we compared the homing performances of homing pigeons that fly singly and in groups of three. Our findings show that although small groups were either governed (i.e. when individuals in the flock had age differences) or not (i.e. when individuals in the flock had the same age) by leaders, with concern to decision-making they were all ruled by democratic decisions. Moreover, the individual homing performances were not associated with leadership. Because true leaders did not assume right away the front position in the flock, we suggest that as in human groups, starting from a central position is more effective as it allows leaders to not only transmit their own information but also to average the tendencies of the other group members. Together, the results highlight the importance of democratic decisions in group decision-making.
- Differential annual movement patterns in a migratory species: Effects of experience and sexual maturationPublication . Jorge, Paulo; Sowter, David; Marques, Paulo A. M.Some animals migrate long distances to exploit important seasonal food resources in the northern regions of the northern hemisphere, whilst avoiding winter starvation. Changes in the individual’s age and navigational skills are likely to affect migration, which in turn influences the geographic distribution of individuals. Processes such as sexual maturation and navigational abilities are affected by age, and age is thus a key factor in understanding migration patterns and differences in distribution ranges. In the present study, we investigated the effects of age on the geographic distribution of a population of Lesser Black-backed Gulls Larus fuscus throughout its annual cycle, by analyzing a dataset of 19,096 records from 10,000 color-ringed gulls. In contrast to previous assumptions, the results showed that gulls were geographically segregated by age throughout the entire annual cycle, rather than showing a geographic age-related cline only in the wintering areas. This asymmetric distribution results from a reduction in the annual range of sexually mature gulls, and the differential distribution of mature and immature individuals (mature birds remained in more northern areas, compared to immature birds, throughout the annual cycle). Furthermore, although immature gulls travelled longer distances than adults, they initiated their fall migration with short movements, in contrast to adults that migrated using longer movements. The effects identified in this study explain the non-homogenous distribution of populations throughout the annual cycle, with wide implications for the development of effective human health policies and/or wildlife management strategies.
- From the past to the future : Natural sound recordings and the preservation of the bioacoustics legacy in PortugalPublication . Marques, Paulo A. M.; Magalhães, Daniel M; Pereira, Susana F.; Jorge, PauloThe preservation of historical and contemporary data safeguards our scientific legacy. Bioacoustic recordings can have historical as well as scientific value and should be assessed for their conservation requirements. Unpreserved bioacoustics recordings are generally not referenced and are frequently at high risk of loss by material degradation and/or by misplacement. In this study we investigated the preservation status of sets of natural sound recordings made in Portugal from 1983 until 2010 inclusive. We evaluated the recordings on the basis of their rate of loss, the degree to which unpreserved recordings could be preserved, and their risk of loss. Recordists of animal sounds were surveyed (by questionnaire or interview) to identify sets of recordings and to collect information on their quality and state of preservation. Of the 78 recordists identified, we found that 32% of the recordings have an unclear status and that only 9% of the recordings are lost. Of the c. 6 terabytes of unpreserved sound recordings discovered, an estimated 49% were recoverable. Moreover, 95% of the recoverable sets of recordings were at high risk of loss by their being misplaced. These risks can be minimized if recordists are persuaded to deposit their material in an institution committed to long-term curation of such data (e.g. sound archives). Overall, the study identified a considerable body of unpreserved animal sound recordings that could contribute to our scientific heritage and knowledge of the biodiversity found in Portugal. It highlights the need to implement effective policies to promote the deposit of recordings for preservation and to reverse the present scenario so that scientific material can be preserved for future generations.
- Gulls can change their migratory behavior during lifetimePublication . Marques, Paulo A. M.; Sowter, David; Jorge, PauloMigration is a widespread phenomenon among birds and is likely to be subject to strong selective pressures. Birds’ annual routines and behaviors might be expected to change during their diff erent life history stages, resulting in diff erent, agerelated migration patterns. However, although migration has been the subject of many publications, age-related diff erences in migration have received little attention. Th e present study examined age-related changes in individual migration habits in lesser black-backed gulls, Larus fuscus. We analyzed data from 10-year (1998–2007) color-ringing project in NW England, comprising more than 10 000 ringed individuals. Our results showed a latitudinal cline in age structure across the wintering range, with adults and gulls in their fi rst breeding year wintering closer to the breeding grounds. Supporting this result we observed that individuals, as they get older, changed the migration behavior and winter closer to the breeding areas. Interestingly, we found no diff erences in survival rates across the wintering grounds. Th us diff erences in survival rates can not account for the latitudinal cline in age structure, and the observed fi ndings seem to be best explained by the arrival time hypothesis, based on a mechanism whereby individuals are able to change their migratory behavior as result of the onset of sexual maturity and associated mating pressures.
- Home sweet home: evidence for nest-fidelity in the rocky intertidal fish, the shanny Lipophrys pholisPublication . Martins, Joana; Almada, Frederico José Oliveira de; Gonçalves, Ana Sofia Ribeiro; Coelho, Pedro Duarte; Jorge, PauloThe ability to be faithful to a particular area or site was analysed in the shanny Lipophrys pholis. Using passive integrated transponders, adults from a population of L. pholis at Cabo Raso, Portugal, were followed over a period of 3 years. The findings showed that site fidelity is a consistent behaviour during the breeding season with specific breeding males being found only in particular sectors within the area, and in specific nests throughout the years. The fact that, in general, L. pholis individuals were absent from the study area during the non-breeding season and breeding males were recorded returning to the same nests and sectors for consecutive breeding seasons suggests that they have developed excellent homing abilities. Translocation data corroborate this idea showing that breeding males successfully returned to their nests after a displacement of >100 m. Altogether, these findings highlight the relevance of life-history traits (e.g. nesting) in the conditioning of site fidelity and homing for this species of rocky intertidal fish, and more importantly, provide evidence for the need of a well-developed navigational system.
- Homing in rocky intertidal fish. Are Lipophrys pholis L. able to perform true navigation?Publication . Jorge, Paulo; Almada, Frederico José Oliveira de; Gonçalves, Ana Sofia Ribeiro; Coelho, Pedro Duarte; Almada, Vítor CarvalhoAlthough navigation is common in many animals, only a few perform true navigation, meaning that they have the ability to return to a given place by relying on indirect cues obtained at the release site (i.e., by relying on information from a ‘‘map and compass’’ mechanism). The common intertidal fish, Lipophrys pholis, is thought to have homing abilities through a mechanism that primarily makes use of familiar landmarks (i.e., piloting). Anecdotal reports that individuals return to their home pools after release at unfamiliar sites suggest that L. pholis might use cues collected at the release site to find their way back (i.e., they might use map and compass information). Using a completely artificial setup, we tested the homing abilities of L. pholis as a function of age, sex, and familiarity with the release site. The findings showed that motivation for homing is present only in the adult phase and is independent of sex and/or familiarity with the release site. Moreover, adults released at a completely unfamiliar place oriented themselves in a direction roughly similar to that of their home pools. The fact that L. pholis were tested in a complete artificial environment means that hydrodynamic cues can be excluded as playing a role in this process and restricts the candidate options (e.g., magnetic cues). The ability to perform navigation based on a ‘‘map and compass’’ mechanism raises many interesting questions about the learning process, once these individuals have restricted home ranges during their lives. In vertebrate navigation, the cues used during the navigation process are a question of debate, and L. pholis offers an outstanding model to test hypotheses and ultimately provide answers.
- Light-dependent magnetic compass orientation in amphibians and insects: candidate receptors and candidate molecular mechanismsPublication . Phillips, John B.; Jorge, Paulo; Muheim, RachelMagnetic compass orientation by amphibians, and some insects, is mediated by a light-dependent magnetoreception mechanism. Cryptochrome photopigments, best known for their role in circadian rhythms, are proposed to mediate such responses. In this paper, we explore light-dependent properties of magnetic sensing at three levels: (i) behavioural (wavelength-dependent effects of light on magnetic compass orientation), (ii) physiological (photoreceptors/photopigment systems with properties suggesting a role in magnetoreception), and (iii) molecular (cryptochrome-based and non-cryptochrome-based signalling pathways that are compatible with behavioural responses). Our goal is to identify photoreceptors and signalling pathways that are likely to play a specialized role in magnetoreception in order to definitively answer the question of whether the effects of light on magnetic compass orientation are mediated by a light-dependent magnetoreception mechanism, or instead are due to input from a non-light-dependent (e.g. magnetite-based) magnetoreception mechanism that secondarily interacts with other light-dependent processes.
- Olfactory navigation: Failure to attempt replication of critical experiments keeps controversy alive: Reply to WallraffPublication . Phillips, John B.; Jorge, PauloInexistente