How to weigh an elephant seal with one finger: a simple three-dimensional photogrammetric application

Bruyn, P. J. Nico de; Bester, Marthán N; Carlini, Alejandro R; Oosthuizen, W. Chris

doi:10.3354/ab00135

Cited by 52 publications

(107 citation statements)

References 28 publications

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“…Seals lying on boards represent a "best case" scenario, and even in this case it is difficult to reproduce measures of seal length to within 2%. Multiple imaging solutions to create three-dimensional images are possible, but seals are notoriously difficult to measure consistently even when they are captured and chemically restrained (e.g., de Bruyn et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Assessing use of and reaction to unmanned aerial systems in gray and harbor seals during breeding and molt in the UK

Pomeroy

O’Connor

Davies³

2015

J. Unmanned Veh. Sys.

117

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Wildlife biology applications of unmanned aerial systems (UAS) are extensive. Survey, identification, and measurement using UAS equipped with appropriate sensors can now be added to the suite of techniques available for monitoring animals -here we detail our experiences in using UAS to obtain detailed information from groups of seals, which can be difficult to observe from land. Trial flights to survey gray and harbor seals using a range of different platforms and imaging systems have been carried out with varying success at a number of sites in Scotland over the last two years. The best performing UAS system was determined by site, field situation, and the data required. Our systems routinely allow relative abundance, species, age-class, and individual identity to be obtained from images currently, with measures of body size also obtainable but open to refinement. However, the impacts of UAS on target species can also be variable and should be monitored closely. We found variable responses to UAS flights, possibly related to the animals' experience of previous disturbance.Key words: UAS, wildlife, seals, photo-ID, photogrammetry, behaviour.Résumé : L'utilisation des systèmes aériens sans pilote (UAS) en biologie faunique ne cesse d'augmenter. Les levés, l'identification et les mesures utilisant les UAS munis de capteurs appropriés font maintenant partie de l'ensemble des techniques disponibles pour surveiller les animaux -ici, nous exposons en détail nos expériences d'utilisation des UAS pour obtenir des informations détaillées sur des groupes de phoques, qui peuvent être difficiles à observer à partir de la terre. Des vols d'essais pour faire le levé des phoques gris et communs utilisant une gamme de plateformes et de systèmes d'imagerie ont été réalisés avec un niveau de succès varié à un nombre de sites en Écosse au cours de deux dernières années. On a déterminé l'UAS le plus performant selon le site, la situation sur le terrain et les données requises. Nos systèmes permettent de couramment obtenir l'abondance relative, les espèces, la classe d'âge et l'identité particulière à partir d'images, y compris les mesures de la masse corporelle mais pouvant être perfectionnées. Cependant, les effets des UAS sur les espèces ciblées peuvent varier et doivent être surveillés de près. Nous avons trouvé des réactions variées aux vols d'UAS, probablement lié à l'expérience des animaux suite à des perturbations antérieures.Mots-clés : système aérien sans pilote (UAS), faune, phoques, photo-identificateur, photogrammétrie, comportement.

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Section: Discussionmentioning

confidence: 99%

Assessing use of and reaction to unmanned aerial systems in gray and harbor seals during breeding and molt in the UK

Pomeroy

O’Connor

Davies³

2015

J. Unmanned Veh. Sys.

117

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“…Photographs of unrestrained adult females were taken with calibrated cameras as described in de Bruyn et al (2009). Photogrammetry was performed with calibrated SLR (single-lens reflex) cameras (Canon 350D,400D and 450D).…”

Section: Photogrammetrymentioning

confidence: 99%

Age-related reproductive variation in a wild marine mammal population

2013

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Life history theory predicts a change in reproduction success with age as energy resources are limited and must be allocated effectively to maximise reproduction and survival. In this study we use three reproductive performance measures; maternal expenditure, offspring weaning mass and first year survival to investigate the role maternal age plays in successful reproduction. Long-term uninterrupted life history data available for Marion Island's southern elephant seals and mass change estimates from photogrammetry data allow for assessment of age related reproduction performance and trade-offs. Known-aged adult females were photographed for photogrammetric mass estimation (n=29) and their pups weighed at weaning during the 2009 breeding season. Maternal age and proportional mass loss positively influenced pup weaning mass. In turn first year pup return rates (as a proxy for survival) were assessed through the intensive mark-recapture program.Pup survival increased with female age and weaning mass. Pups of young females aged 3 to 6 years have a lower 1 st year survival probability compared to pups of older and larger females.

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“…This research area offers unique opportunities for innovative and leading engineering studies; within the South African context this field is largely unexplored. Furthermore, the challenging field conditions for biological research also promote creativity and ingenuity in the use and development of novel technologies 33 that can be applied more broadly 34 .…”

Section: Technology and Engineeringmentioning

confidence: 99%

Exploring South Africa’s southern frontier: A 20-year vision for polar research through the South African National Antarctic Programme

Ansorge¹,

Skelton²,

Bekker³

et al. 2017

S. Afr. J. Sci.

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How to weigh an elephant seal with one finger: a simple three-dimensional photogrammetric application

Cited by 52 publications

References 28 publications

Assessing use of and reaction to unmanned aerial systems in gray and harbor seals during breeding and molt in the UK

Assessing use of and reaction to unmanned aerial systems in gray and harbor seals during breeding and molt in the UK

Age-related reproductive variation in a wild marine mammal population

Exploring South Africa’s southern frontier: A 20-year vision for polar research through the South African National Antarctic Programme

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