Browsing by Author "Hartman, Karin L."
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- Behavioural responses of Risso’s dolphin, Grampus griseus, to remote biopsy samplingPublication . Hartman, Karin L.; Wittich, Anja; Neves, Dalia; Azevedo, José M. N.Biopsy sampling from free-ranging cetaceans is a widespread method used in various biological studies. Since this is an intrusive research technique, it’s important to determine its impact. We examined the short-term behavioural reactions of Risso’s dolphins, Grampus griseus (2.6-4m in length), off Pico Island, to remote biopsy sampling. Biopsies were conducted over a consecutive two year period using a crossbow with Finn Larsen bolts and tips. Sampling followed a number of precautionary rules, including taking samples only in calm seas, when animals were travelling; no more than 1-4 shots per group; and females with nursing calves were not exposed to sampling. Behavioural responses were analysed by visual observation using two scales of behavioural reactions: i) the reaction of the targeted individual, and ii) the reaction of the focal group to which the targeted individual belonged. We defined five categories of intensity of behavioural response (none, low, medium, high, very high) and five types of display response (quick dive, QD; diving & leaving, D&L; jumping, J; tail slapping, TS; and speeding away at surface, SS). A total of 189 shots were made (115 hits, 74 miss) during 61 survey days. Tissue was obtained in 83% of the hits. No significant differences were found between hits and misses in behavioural responses or types of display (Kruskal Wallis test). In 9% of the cases there was no visible reaction, while most (48%) behavioural responses were of low intensity. The frequencies of the display responses differed significantly from each other (chi-squared test). The types QD and D&L constituted 79% of the responses. Group reaction was observed during 1/5 of the shots, (main behaviour D&L-51%). Although biopsy sampling is an invasive method, our results indicate that if basic precaution rules are followed low intensity behavioural responses can be expected for half of the time.
- Data analysis model selection for estimating local population size of the Risso’s dolphin (Grampus griseus) in the AzoresPublication . Stap, Tim Van der; Hartman, Karin L.; Wittic, Anja; Azevedo, José M. N.; Heitkönig, Ignas M. A.Different models estimating cetacean population size require making assumptions about the marking and recapturing of individuals, and on the structure of the population. Crucial in selecting the most appropriate model is a critical assessment of these assumptions. In this study we applied the robust parameterization of the open Jolly-Seber (JS) model (POPAN), using the software program MARK. This model was applied to data collected on the Risso’s dolphin (Grampus griseus). Between 2004 – 2007, photo-identification was used as a Capture-Mark-Recapture technique to identify 670 unique individuals off Pico Island, Azores. For this model, it was assessed what assumptions are supported or violated. The aim of this study was improving our understanding of how to select the most appropriate population size model.
- Differences in spatial distribution of two small delphinids (Delphinus delphis and Stenella frontalis) in two islands of the Azores ArchipelagoPublication . Fernandez, Marc; Oviedo, L.; Hartman, Karin L.; Sousa, B.; Azevedo, José M. N.The archipelago of the Azores represents a special area of cetacean ocurrence, mostly due to its oceanic nature. In this area two small delphinids, the common dolphin and the Atlantic spotted dolphin, the former seeming to be present all year around, while the latter seems to be seasonal (summer). In this study we analyse their respective distribution in two different islands, Pico and São Miguel. Sighting records from 2005 to 2008 in Pico, and from 2008 in São Miguel, were pooled together, analyzed and incorporated into a Geographic Information System (ArcGis 9.3). In order to understand the relations between these species and the ecogeographical variables, a statistical treatment (Kruskal-Wallis) and an Ecological Niche Analisis (using Biomapper 4) were perfomed. While common dolphins and Atlantic spotted dolphins are statistically related with depth and slope in Pico, they are just statiscally related with depth in São Miguel. Moreover there are statiscal differences between their distribution in the two islands, suggesting differences on the ecological niche of the species depending on the island, probably related with differences on bathymetry features. There are also differences in distribution between common dolphins and Atlantic spotted dolphins in São Miguel, while in Pico they seem to cohabit in the same area, possibly indicating a niche overlap. In São Miguel, statiscal differences in the distribution between the two species (in depth and in slope) are present, atlantic spotted dolphins showing more tolerance to deep waters. These results suggest the existence of differences on these two delphind populations’ distributions depending on the island, probably due to different bathymetric features. Further work is being conducted in order to better understand their distribution and interactions.
- Habitat differentiation between groups of Risso's dolphins as evidence of coastal nursery areasPublication . Fernandez, Marc; Hartman, Karin L.; Azevedo, José M. N.Previous studies have shown strong site fidelity by Risso's dolphins at a site off Pico Island, Azores. Females with calves tend to be seen together, often with newborn calves. In this study we analyse position and photo-identification data gathered on ocean surveys from 2004 to 2007 to look at the distribution of females with calves of different ages (newborns to 6 months old, 6 months to 2 years and 2 to 4 years) and compare it with pods with no calves present. The association of the different groups with selected ecogeographical variables was tested, and a maximum entropy model was used to create habitat suitability maps, using a 50mx50m grid. The female pods with younger calves were found to have a significantly distinct distribution from those with older calves or without calves. The main difference was that the pods with younger calves tended to be found closer to the shore, whereas the other groups used a wider offshore area. More extensive sampling is required in order to validate the existence and geographical distribution of coastal nursery areas for this species. However, we believe the present data is enough to elicit precautionary conservation measures to reduce human impact on a vulnerable part of the dolphin society, such as that associated with boat traffic, whale watching and swimming with dolphins operations.
- Large-scale movements of common bottlenose dolphins in the Atlantic : dolphins with an international courtyardPublication . Dinis, Ana; Molina, Carlota; Tobeña, Marta; Sambolino, Annalisa; Hartman, Karin L.; Fernandez, Marc; Magalhães, Sara; Santos, Rui Peres dos; Ritter, Fabian; Martín, Vidal; Aguilar de Soto, Natacha; Alves, Filipe M. A.Wide-ranging connectivity patterns of common bottlenose dolphins (Tursiops truncatus) are generally poorly known worldwide and more so within the oceanic archipelagos of Macaronesia in the North East (NE) Atlantic. This study aimed to identify long-range movements between the archipelagos of Macaronesia that lie between 500 and 1,500 km apart, and between Madeira archipelago and the Portuguese continental shelf, through the compilation and comparison of bottlenose dolphin's photo-identification catalogues from different regions: one from Madeira (n = 363 individuals), two from different areas in the Azores (n = 495 and 176), and four from different islands of the Canary Islands (n = 182, 110, 142 and 281), summing up 1791 photographs. An additional comparison was made between the Madeira catalogue and one catalogue from Sagres, on the southwest tip of the Iberian Peninsula (n = 359). Results showed 26 individual matches, mostly between Madeira and the Canary Islands (n = 23), and between Azores and Madeira (n = 3). No matches were found between the Canary Islands and the Azores, nor between Madeira and Sagres. There were no individuals identified in all three archipelagos. The minimum time recorded between sightings in two different archipelagos (≈ 460 km apart) was 62 days. Association patterns revealed that the individuals moving between archipelagos were connected to resident, migrant and transient individuals in Madeira. The higher number of individuals that were re-sighted between Madeira and the Canary Islands can be explained by the relative proximity of these two archipelagos. This study shows the first inter-archipelago movements of bottlenose dolphins in the Macaronesia region, emphasizing the high mobility of this species and supporting the high gene flow described for oceanic dolphins inhabiting the North Atlantic. The dynamics of these long-range movements strongly denotes the need to review marine protected areas established for this species in each archipelago, calling for joint resolutions from three autonomous regions belonging to two EU countries.
- The presence of the sperm whale (Physeter macrocephalus) around the Azores: a study of re-sightings from 2003-2012Publication . Niemeijer, Stella Charlotte; Libotte, Jennifer; Hartman, Karin L.; Steiner, Lisa; Azevedo, José M. N.Aim of the study: Find out if sperm whales that are seen during summer in the Azores are migrant or resident individuals to gain a better understranding of their life history.
- Sex differences in residency patterns of Risso's dolphins (Grampus griseus) in the Azores : causes and management implicationsPublication . Hartman, Karin L.; Fernandez, Marc; Wittich, Anja; Azevedo, José M. N.Knowledge of the residency patterns of marine mammals is an important element for management and conservation strategies. Here we investigate a population of Grampus griseus off Pico Island, Azores. Our data set covers the period 2004–2007, based on at-sea observations of 1,250 individually identified animals, 303 of known or assumed sex. Using photo identification and GPS locations we calculated mean monthly sighting rates and lagged identification rates to analyze temporal patterns, and estimated kernel density to study the home range. Our results show site fidelity and relatively restricted home ranges, which corroborate the existence of a resident population on the study site. We further document sex differences, including a higher number of males present in the area at any given time but females staying for longer consecutive periods, and male home ranges with significantly less overlap than those of females. These observations are consistent with a mating system based on multimale pods defending areas where females periodically return. We hypothesize that squid distribution is a major factor in structuring these patterns. These findings reinforce the need for a precautionary management approach that would include limiting pressure from commercial activities.
- Show me your body and I tell you how hold you are: a non-invasive methodto define 6 life history-classes in Risso's dolphins (Grampus griseus), using an identified trial population in the AtlanticPublication . Hartman, Karin L.; Wittich, Anja; Azevedo, José M. N."[…]. The objective of this paper is to present a new non-intrusive and inexpensive method to classify six life history stages in Risso's dolphins: from newborn calf to old-adult. We propose an age-class indicator model using the scarification patterns and the species unique discoloration process. We developed two methods and tested these among 52 rankers to examine if our proposed methods could be applied by anybody and if they would conform with our age class model. We also investigated the possible differences in the scarification patterns between genders. We used a longterm followed identified population of Risso's dolphins in the Azores to set up our test methods and report our present results."
- Spatial segregation of calving and nursing Risso’s dolphins (Grampus griseus) in the Azores, and its conservation implicationsPublication . Hartman, Karin L.; Fernandez, Marc; Azevedo, José M. N.Calving can be a critical period for cetaceans. Areas providing security for vulnerable calves, and high food availability for lactating females can be critical habitats requiring specific conservation measures. Here, we test the hypothesis that calving and nursing habitat could be defined for Risso’s dolphins (Grampus griseus). We investigated the spatial and temporal preferences of this species around Pico Island, Azores, using data gathered from land-based surveys and dedicated at-sea observations between 2004 and 2007. We divided observed pods into three groups: (1) those with newborn and young calves, (2) those with older calves or juveniles and (3) those consisting only of adults or sub-adults. We analysed eco-geographical variables and incorporated them into a presence-only spatial distribution model to evaluate differences in habitat suitability among the groups. We identified 694 pods of Risso’s dolphins overall. On the 267 pods observed in the first and second groups, 136 calves or juveniles were identified, of which 22 were newborns. The peak of the calving season was between June and August. The pods with newborn calves were larger and closer to shore, whereas the other groups were more widely dispersed offshore. Our results support the definition of critical habitat areas for this species, but we suggest widening the geographical coverage for better mapping around the island and throughout the archipelago generally. Conservation measures can, nevertheless, be implemented immediately, in order to reduce human impacts on a vulnerable component of the Risso’s dolphin population.
- Spatial segregation of calving and nursing Risso's dolphins (Grampus griseus), and its conservation implicationsPublication . Hartman, Karin L.; Fernandez, Marc; Azevedo, José M. N.