Body composition changes, metabolic fuel use and energy expenditure during extended fasting in subantarctic fur seal (Arctocephalus tropicalis) pups at Amsterdam Island

The fasting metabolism of 71- to 235-d-old subantarctic fur seal (Arctocephalus tropicalis) pups from Amsterdam Island, southern Indian Ocean, was investigated during the long foraging trips of their mothers. Body lipid reserves were proportionally greater in female than male pups and higher in postmoult (37%) than premoult (10%) animals. The mass-specific rate of mass loss did not differ between the sexes but was lower than observed in other species. Daily mass loss was estimated to 56% fat, 10% protein, and 34% water. The rate of protein catabolism (15 g d&minus;1) was negatively related to the size of initial lipid stores and accounted for 9% (&plusmn;1%) of total energy expenditure. However, body composition changes during the fast were not equal between the sexes, with females relying more on protein catabolism than males (11% and 5% of total energy expenditure, respectively). Energy expenditure (270 kJ kg&minus;1 d&minus;1) and metabolic water production (11.5 mL kg&minus;1 d&minus;1) rates are the lowest reported for an otariid species. These results suggest that subantarctic fur seal pups greatly reduce activity levels to lower energy expenditure in addition to adopting protein-sparing metabolic pathways in order to survive the extreme fasts they must endure on Amsterdam Island.<br /

Variations des performances de pêche et des performances démographiques des femelles otaries à fourrure de l'île d'Amsterdam (Arctocephalus tropicalis) (influence de la qualité individuelle et des conditions environnementales)

Ce travail décrit dans quelle mesure les traits d'histoire de vie sont liés aux stratégies maternelles de l'otarie à fourrure subantarctique Arctocephalus tropicalis de l'île d'Amsterdam. Pendant l'élevage du petit, les femelles ajustent leur stratégie de pêche (site, budget, proies) aux variations environnementales saisonnières. Les petits subissent des jeûnes prolongés entraînant de faibles taux de croissance. La survie pré-sevrage (69%) ne semble affectée par aucun facteur, alors que la survie post-sevrage (66%) dépend du sexe, du taux de croissance pré-sevrage, et des conditions environnementales au sevrage. La survie juvénile et adulte annuelle élevée (98%) est indépendante de l'année ou de l'environnement, et la sénescence est présente chez les femelles de plus de 13 ans. Les probabilités de survie et de reproduction futures des non-reproductrices sont inférieures à celles des reproductrices, suggérant l'existence d'un phénomène de qualité individuelle au sein de cette population.LA ROCHELLE-BU (173002101) / SudocSudocFranceF

Acoustic analysis of airborne, underwater, and amphibious mother attraction calls by wild harbor seal pups (Phoca vitulina)

International audiencePinnipeds have great potential for comparative studies of mother–pup recognition due to the contrasting maternal strategies adopted by otariids and phocids. Typically, otariid mothers perform foraging trips during lactation, leaving their pups in the colony, whereas phocid mothers remain close by their pups during the entire nursing period. Unlike most phocids, harbor seal (Phoca vitulina) females forage during the nursing period, which exacerbates the need for effective mother–pup vocal recognition in this species. Individual differences and ontogeny-related changes in airborne and underwater harbor seal mother attraction calls were investigated. Acoustic differences between aerial and underwater components of amphibious pup calls were also assessed. Sixteen acoustic parameters were measured on 1,072 calls from 88 pups recorded during the 2011–2013 breeding seasons in the St. Lawrence Estuary, Canada. Discriminant function analysis (DFA) correctly assigned 42.6% and 44.2% of airborne and underwater calls, respectively, to individual pups. A majority of highly individualized acoustic parameters were affected by pup age and body length. These results indicated that harbor seal pup calls encode an individual signature that might allow recognition of young by mothers, in which case females must continuously learn their pup’s changing voice throughout of the rearing period. The fundamental frequency, total duration, and frequency-modulation slopes were constant between aerial and underwater components of amphibious calls. This could facilitate females’ memorization of these highly individualized acoustic parameters to identify their offspring’s call in both media

Factor matrix from varimax-rotated component analysis on PDER events (<i>n</i> = 1267) recorded in nursed harbour seal pups.

<p>Factor matrix from varimax-rotated component analysis on PDER events (<i>n</i> = 1267) recorded in nursed harbour seal pups.</p

Characteristics of PDERs generated by different ingestion types.

<p>A: a PDER event where points <i>A</i>, <i>B</i> and <i>C</i> are showed (see text for definitions), in addition to the amplitude of temperature drop (<i>T_A</i>-<i>T_B</i>), duration from <i>A</i> to half-way temperature recovery (<i>t_0.5</i>) and temperature at half-way temperature recovery (<i>T_0.5</i>), indicated by a black point on the Y axis. B: From left to right; PDER events associated with seawater, solid food and milk ingestions, respectively, extracted from a harbour seal pup stomach temperature record. C: Expected order of magnitude for 6 stomach temperature variables.</p

Summary of PCA on 6 stomach temperature variables associated with PDER events (<i>n</i> = 1269) recorded in nursed harbour seal pups.

<p>Summary of PCA on 6 stomach temperature variables associated with PDER events (<i>n</i> = 1269) recorded in nursed harbour seal pups.</p

Distribution of the PDER events (<i>n = </i>1776) recorded in nursed harbour seal pups (<i>n</i> = 35) equipped with TDRs and STPs among individuals and ingestion types.

a<p>Percentage of total ingestions.</p

<b>Table 5.</b> Summary of the linear discriminant analysis on 6 stomach temperature variables for PDER events (n = 1268) resulting from ingestion in nursed harbour seal pups.

<p><b>Table 5.</b> Summary of the linear discriminant analysis on 6 stomach temperature variables for PDER events (n = 1268) resulting from ingestion in nursed harbour seal pups.</p

Characteristics of harbour seal pups (<i>n</i> = 40) equipped with STPs during the 2010–2012 nursing periods at Bic Island, Quebec, Canada.

1<p>Stomach temperature records empty, either due to pill transmission failure or pill lost by animal.</p>2<p>Found dead on the shore following an episode of extreme wave conditions.</p

Distribution of the <i>I</i> index of PDER events (<i>n</i> = 190) from groups 2 and 4.

<p>When compared to preliminary visual classification, 98.9% of the PDER events having <i>I</i> index values lower than 92.8 s°C⁻¹ had been deemed seawater ingestions, while 92.3% of the PDER events with <i>I</i> index values greater than 92.8 s°C⁻¹ had been deemed solid food ingestions.</p