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The Ross Sea in the Southern Ocean is frequently considered one of the most pristine ecosystems in the world, but recent data suggest that changes to oceanic conditions may be impacting wildlife abundance. We used 41 yr of data to assess how variation in biologically relevant environmental conditions relates to annual reproductive output for the world’s largest population of Weddell sealsLeptonychotes weddellii, an upper-level predator in the Ross Sea. Pup production increased 150% across the time series, and interannual variation tripled. Linear regression analyses, which explained 73.7% of the variance in pup production, supported a non-linear, convex relationship between reproductive output and summer sea ice extent, with more pups born in years with more or less sea ice than in years with intermediate ice extent. While total annual toothfish catch 7 yr previous appears to be positively associated with reproductive output, a similar amount of variation in pup production could be explained by an alternative model with a linear, temporal trend. Our results highlight a sizable increase in the reproductive output of this demographically buffered polar marine predator. The increase in pup production may be the result of competitive release due to commercial fishing, cascading ecological effects from commercial fishing or other environmental shifts, or population inertia from a few large birth cohorts. It is challenging to disentangle these hypotheses with the current publicly available environmental data. Future demographic analyses and collaborative research are needed to understand how environmental changes are impacting marine populations in this ecosystem. 

Abstract Pigmentation and colouration are important to animal fitness. Colourations convey important information and impact predation risk, thermoregulation and mate selection. There are many cases of hypopigmentation across the animal kingdom, and leucism is a common form. We observed a Weddell seal (Leptonychotes weddellii) pup with cream-coloured fur, light skin and white nails multiple times in 2022 in Erebus Bay, Antarctica. The pup was observed 1 year later as a generally healthy yearling. This is the first documentation of a leucistic seal within this well-studied population and the second documentation of such colouration in this species. This seal offers a potential opportunity to observe the effects of hypopigmentation in Antarctic true seals. 

Abstract A wide variety of nipple locations and configurations exist among pinnipeds. Like all marine mammals, pinnipeds can have supernumerary nipples that form in utero. Supernumerary nipples have been documented in several species of pinnipeds, the only taxonomic group of marine mammals with variation in nipple number. We document multiple observations (n = 4) of female Weddell seals (Leptonychotes weddellii) with supernumerary nipples in Erebus Bay, Antarctica, including a female Weddell seal with four nipples that was observed nursing two pups. Intraspecific variation in the number of supernumerary nipples observed included both one and two supernumerary nipples. The majority of the observed supernumerary nipples were nursed on by pups, but lactation was unable to be confirmed. These are the first documented observations of supernumerary nipples in Weddell seals.