A new application for transponders in studying penguins

Transcription

1 J. Field Ornithol. 76(2): , 2005 A new application for transponders in studying penguins Jean-Paul Gendner, 1 Michel Gauthier-Clerc, 1,2,3 Celine Le Bohec, 1 Sebastien Descamps, 1 and Yvon Le Maho 1 1 Centre d Écologie et Physiologie Énergétiques CNRS, 23 rue Becquerel, Strasbourg cedex 2, France 2 Station Biologique de la Tour du Valat, Le Sambuc, Arles, France Received 5 January 2004; accepted 12 August 2004 ABSTRACT. We developed an identification setup enabling automatic detection of the passage of free-living King Penguins implanted with small radio frequency transponders at Possession Island, Crozet Archipelago. An unique feature of the system is the use of antennas allowing automatic detection and identification on pathways up to 8-m wide without the use of flipper bands. We present results on demographic parameters of the King Penguin, and we found an unexpectedly survival rate of immature penguins. Such an identification system can be used for other birds, mammals, or reptiles that use regular pathways. SINOPSIS. Un nuevo uso de equipo electrónico (transponders) para estudiar pingüinos Desarrollamos un escenario de identificación, que automaticámente detecta el paso de Pingüinos Emperadores (Aptenodytes patagonicus) a los cuales se le implanto un pequeño radiotransmisor (transponder). El trabajo se llevó a cabo en la isla Posesión, del archipiélago Crozet. Un aspecto único del sistema es el uso antenas que permiten la detección e identificación automática en un área de unos 8 m. de ancho sin el uso de anillas. Presentamos los resultados de parámetros demográficos del ave. Encontramos, sin esperarlo, una tasa alta de sobrevivencia de los pingüinos inmaduros. Dicho sistema de identificación puede ser utilizado para otras aves, mamíferos o reptiles que utilicen un trayecto o ruta regular para moverse. Key words: Aptenodytes patagonicus, demographic parameters, King Penguin, survival, transponders Penguins are intensively studied and used as bioindicators of change in marine ecosystems. Studies of the penguin breeding cycle have generally been based on the use of flipper bands. Although time consuming, this method has been the only practical way to study penguins. However, in addition to a potential loss of flipper bands over the years, there is increasing concern that bands might be detrimental to penguins (Culik et al. 1993; Froget et al. 1998; Jackson and Wilson 2002; Gauthier-Clerc et al. 2004). Our present knowledge of certain key penguin life-history traits should be re-evaluated if the data were obtained from banding studies. We present here a new method for studying the breeding biology and population dynamics in penguins without relying on external marks and show results on demographic parameters of the King Penguin (Aptenodytes patagonicus). 3 Corresponding author. gauthier-clerc@ tourduvalat.org METHODS Study area and monitoring system. Ongoing work was begun in March 1998 at the Baie du Marin in a colony of about 25,000 breeding pairs of King Penguins on Possession Island (46 25 S, E), Crozet Archipelago. An area comprising some 10,000 pairs is connected to the sea by three pathways. Two 8-m long antennas separated by 1 m allowing detection of Radio Frequency IDentification (RFID) transponder tags (TIRIS, Texas Instruments Registration and Identification System) were buried permanently on each pathway and connected to a computerized reading system which collected the data (see Fig. 1). This system differs from other systems developed for penguins (in King Penguins: Gendner et al. 1992; Olsson 1998; Gauthier-Clerc et al. 2001; in Adélie Penguins Pygoscelis adeliae, Clarke and Kerry 1998). Previously, a single detection antenna (30 cm 30 cm) was placed vertically on a gate, and these earlier systems were limited by the small area covered (about 80 cm 80 cm). Our underground antenna system allowed 138

2 Vol. 76, No. 2 Using Transponders With Penguins 139 Fig. 1. Schematic description of the automatic identification system. for surveying a pathway up to 8-m wide via an electromagnetic field 40-cm high. We chose not to band the penguins in order to avoid inducing possible bias in their breeding cycle (Gauthier-Clerc et al. 2004). The battery-free transponder tags, implanted under the skin between the leg and tail of the bird, have a 19-digit identification code, consist of a small cylinder 3.9 mm diameter and 32 mm long, and weigh 0.8 g. The pseudo-passive tags are activated electromagnetically by the antennas at a distance up to 100 cm and allow individual identification of the fitted birds throughout their lifetime. The sequence of signals received by the two antennas determines if a bird is entering or leaving its breeding site. These tags have no known adverse effects (Michard et al. 1995; Froget et al. 1998) if they are correctly implanted (Clarke and Kerry 1998). This identification system does not require bird recapture or visual observation by a human and allows continuous automatic data collection. Consequently, it reduces human presence the disturbance to the birds that results. Breeding adults (about 750 individuals) and cohorts of 10-mo old chicks (about 1400 individuals) were fitted from 1998 to 2002 with transponders leaving no external marks. The system has collected data continuously and automatically day and night over the years , enabling us to follow the complete breeding cycle (see Descamps et al. 2002). Video recording. A video camera was installed on the most important of the three pathways where 90% of penguin passages occurred. Recordings were taken when the transponded birds passed over the antennas so as to determine their body and plumage conditions. This allowed us to differentiate among stages of the breeding cycle (e.g., chick rearing, molting, or displaying). RESULTS AND DISCUSSION In the sample of 542 adults fitted with transponders from March 1998 to March 2000, only one bird was not detected during a summer, and it was detected the following summer. If we had limited our detection sessions to only the summer months of January to March, the probability of detecting a bird would have been near 1.0, provided it remained alive. The recapture rate is also near 1.0, and consequently the reliability of survival estimators should be high (Pollock et al. 1990; Lebreton et al. 1992). This system of automatic identification satisfies the assumptions of the known-fate model, assuming that there are no nuisance parameters

3 140 J.-P. Gendner et al. J. Field Ornithol. Spring 2005 Fig. 2. Survival curves for male (N 89) and female (N 72) adult King Penguins using a Cox proportional hazards model with right-censoring and assuming the last month a bird was detected was the last month it was alive. Months are based on the initial marking month of December 1998 (e.g., mo after marking). involved with the captures (White and Burnham 1999). This system has enabled us to determine and compare annual life-history traits: such as arrival date, foraging trip duration at sea during incubation, brooding and winter periods, feeding frequency of chicks, duration of chick rearing, inter-annual return rates of adults and immatures, and reproductive success (Descamps et al. 2002). It should permit studying life-history strategies and population dynamics through the estimation of demographic parameters and their variability. Considering the group of 50 adults microtagged in February 1998, birds produced a mean of 0.27 chicks per adult per season from 1998 to To illustrate the potential of the system, we examined differences in survival between sexes in the large sample of adults microtagged in December We were able to sex 72 females and 89 males. There was no significant difference between survival curves for males and females (Fig. 2; likelihood ratio test 0.572, df 1, P 0.45). The major decline in survival for both sexes was during May August, during which 71% of the last detections occurred. In the cohorts from 1998 (N 100 chicks) and 1999 (N 200 chicks), 81% of fledged young returned to the studied part of the colony after three winters and 74.5% after two winters. Only 20 25% of 2-yr old immatures were detected in the colony. The maximum presence in the colony occurred among birds 4 yr or older (Fig. 3). It is possible to distinguish two peaks of detection each year corresponding to the molting and courtship periods. This new identification system facilitates survival estimates. It allows re-evaluating demographic parameters previously estimated with banded birds. The system is being used with success and allows a life-history approach to population dynamics for penguins and probably for other taxa. Long-term data on wild animals is difficult to obtain, and bias due to marking techniques is common (Cuthill et al. 1997; Johnsen et al. 1997; Gauthier-Clerc and Le Maho 2001). The transponder system described here overcomes some of those biases for penguins. ACKNOWLEDGMENTS This work was supported by the Institut Polaire Français Paul-Emile Victor (Programme 137) and by the project Zones Ateliers of the Programme Environnement Vie et Société of the CNRS. We thank Alexandre Rosinski, Nicolas Chatelain, Jean-Charles Fournier, Grégoire Kuntz, Nicolas Lambert, Nicolas Lecomte, Step-

4 Vol. 76, No. 2 Using Transponders With Penguins 141 Fig. 3. Number of birds of the 1998, 1999, 2000, 2001 and 2002 cohorts detected by month for four years. Cohort 1998, N 100 chicks; cohort 1999, N 200 chicks; cohort 2000, N 418 chicks; cohort 2001, N 391 chicks; cohort 2002, N 300 chicks. han Mangin, Vincent Motsch and Alexandre Rosinski for their help in the field and C. Salmon for his help in preparing software for the data analysis. William R. Fraser and Eric J. Woehler improved the manuscript with critical comments. This study was approved by the Ethics Committee of the Institut Polaire Français Paul- Emile Victor and followed the Agreed Measures for the Conservation of Antarctic and Subantarctic Fauna. LITERATURE CITED CLARKE, J., AND K. KERRY Implanted transponders in penguins: implantation, reliability, and long-term effects. Journal of Field Ornithology 69: CULIK, B. M., R. P. WILSON, AND R. BANNASCH Flipper-bands on penguins: what is the cost of a long-life commitment? Marine Ecology Progress Series 98: CUTHILL, I. C., S. HUNT, C.CLEARY, AND C. CLARK Colour bands, dominance, and body mass regulation in male Zebra Finches (Taeniopygia guttata). Proceedings of the Royal Society of London B 264: DESCAMPS, S., M. GAUTHIER-CLERC, J.-P. GENDNER, AND Y. LE MAHO The annual breeding cycle of unbanded King Penguins Aptenodytes patagonicus on Possession Island (Crozet). Avian Science 2: FROGET, G., M. GAUTHIER-CLERC, Y.LE MAHO, AND Y.

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