Lydie,

One method of home range estimation is kernal density estimation, where an animals home range is typically taken as the 95% contour of the utilisation distribution. See: Seaman, D.E. & Pwell, R.A. (1996). An evaluation of the accuracy of kernal density estimators for home range analysis. Ecology 77, 2075-2085.

Hope this helps,

Viki

I think that the term home range refers to the area in which is more suitable for the living of the elasmobranch. It´s related to physical characteristics of the environment/habitat where the animal live.

Ultimately depends on what questions you are asking as the home range of large, free-ranging marine animals can vary temporally. You could consider the different locations (foraging grounds?) as core areas within a larger home range area. The kernel density estimator and others can give increasing smaller levels of utilization (95%, 75%, 50%, etc.) for identifying core areas.

I think what Lydie question may need to be considered from the theory of patches. Regards

Dear

Home range is a large area also unpredictable because marine animals are free-ranging consider the different (changing) locations like foraging grounds and breeding ground, water current also influence the home range. Marine animal not easy to tel area,this is a home range

From the point of view of being human. This planet is our home. But are we only limited to the human body is another question. So anyhow the question remains what are we. Or as individuel ' who am I'; ?

Dear Lydie,

I would say it depends on the biology and ecology of the species under study. Many of these definitions were made for terrestrial species; also, they seldom incorporate the possibilities of metapopulations or patchy distributions. For instance,

Burt (1943) described the home range as the area travelled by an individual while developing its regular activities of feeding, mating and calving.

Jewell (1966) said its an area with certain productivity that fulfills the energetic requirements of individuals or groups.

Bailey (1984) defined it as the area travelled by an individual while developing its regular activities excluding migrations, exploration or erratic movements.

Reynolds et al. (2000) consider it is a well defined and regularly used area that provides most if not all the requirements of the individual.

Instead, I have found helpful the use the concept "utilization distribution" which refers to the amount of time spent by an individual in a given place (Jennrich y Turner, 1969). It implies a probabilistic approach for the "home range" that describes the relative frequency of the location of an animal in a given time (Van Winkle, 1975). Such frequencies may be transformed to densities as they are standardized by the area, and can be useful to determine overlapping individuals, populations or species in terms not only of their distribution, but also the intensity of the use at specific places (Seaman & Powell, 1996). However, as Karuppiah Kannan detailed, you need to determine if your spatial and temporal scales are appropriate to use your data as a proxy for the home range.

As Victoria Wearmouth and Jeffrey Schmid wrote, the kernel method has been widely used for a wide range of species, but the selection of the analyses will depend on the kind of data you can gather (such that it doesn't violate the assumptions of the model), and according to your specific goals. With this in mind, as Venancio Azevedo wrote, you may choose to incorporate environmental variables that are "known" to have significant influence in the distribution of the species and apply GIS analytical tools to check how they correlate with the actual distribution of your subjects.

I hope this helps....

I would use the concept of home range as part of the concept of *activity field*.

If you could follow an individual animal using telemetry of GPS and obtain positions at regular intervals during several months or years, plotting these positions as a geographical density plot would reveal patterns. Intensity of use of certain geographical zones would reveal structure. But you would need to observe concomittant behavior to define places and zones as territory (defended area), feeding area, reproductive lek, &c. The home range would encompass all these. The outermost points on such a map could be connected to form the smallest possible convex polygon, which could operationally considered as the individual home range. Remember, here the activity field (and thus home range) is generated by one individual. By merging the activity fields of several individuals and studying their overlapping the researcher could construct a comparable concept for several individuals, a local population, or even a species.

Thank you very much everyone for your feedback and for your detailed answer Eduardo Morteo. As Gustavo Chiaramonte said, I am more interested in the theoretical definition of home range and how it applies to marine species and what are the limitations of the use of this term. There seems to be a fair bit of debate on this subject.

In our case, we cannot really use any statistical approaches such as Kernel density to define the home range of the species. We used photo-identification data collected opportunistically for the last 5 years (through citizen science). We found that many of our IDed individuals displayed strong site affinity (visited the same site multiple times over years) to several aggregation sites within a larger area (within 700 km long area along the coast). Similar results were found in other parts of the world. Considering this, would it be appropriate to state that the species appears to have a relatively large home range that includes several aggregation sites?

Home range is the environment span that constitutes the normal/regular navigation of a species or an environment that contains features or niches critical to its survival. For animals that are not long distance swimmers the home range often overlaps with the foraging range.

Elasmobranchs do not fall into the category of long distance swimmers thus are not likely to have a home range as wide as that for stronger swimmers.

Dear Lydie,

I think it would be more appropriate to look at your data in terms of station keeping versus commuting versus migration. An animal's'normal' activity range, including foraging and shelter sites could be defined as its home range. This might include commuting between several 'core areas'. These can be determined by direct or indirect observations i.e. SCUBA, tracking, telemetry etc. Many animals display seasonal migrations linked to reproduction or foraging conditions. A migration is something that is more predictable than 'nomadic' movement and unsually has a predetermined path, endpoint. Very often these movements are repeated anually. From your information it sounds like your animals might migrate, in which case 'homerange' would not really be an appropriate definition. Check out this reference, it is slightly dated but very comprehensive. Dingle, H. 1996. Migration. The biology of life on the move. Oxford University Press,New York.

You may need to consider the use of otoliths in your research. Elemental analysis of the otoliths i.e. otolith microchemistry will give you an idea of environment history and possibly the habitat range.