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Increased human presence in the Arctic may affect its vulnerable ecosystems. Effects on arctic and red foxes provide notable examples. Both have been documented to take anthropogenic subsidies when available, which can change diet and ranging patterns in complex ways that can either benefit or harm populations, depending on the situation. Understanding this complexity requires new tools to study impacts of increasing human presence on endemic mammals at high latitudes. We propose that dental ecology, specifically tooth wear and breakage, can offer important clues. Based on samples of arctic foxes ( Vulpes lagopus (Linnaeus, 1758)) trapped prior to ( n = 78) and following ( n = 57) rapidly growing human presence on the Yamal Peninsula, Russia, we found that foxes trapped recently in proximity to human settlement had significantly less tooth wear and breakage. This is likely explained by a dietary shift from consumption of reindeer ( Rangifer tarandus (Linnaeus, 1758)) carcasses including bone to softer human-derived foods, especially when preferred smaller prey (e.g., West Siberian lemmings, Lemmus sibiricus (Kerr, 1792), and arctic lemmings, Dicrostonyx torquatus (Pallas, 1778)) are unavailable. These results suggest that tooth wear and breakage can be a useful indicator of the consumption of anthropogenic foods by arctic foxes. 

We report a search for a heavy neutral lepton (HNL) that mixes predominantly with${\nu }_{\tau }$. The search utilizes data collected with the Belle detector at the KEKB asymmetric energy$e^{+}{e}^{-}$collider. The data sample was collected at and just below the center-of-mass energies of the$\mathrm{\Upsilon }(4S)$and$\mathrm{\Upsilon }(5S)$resonances and has an integrated luminosity of$915{\mathrm{fb}}^{-1}$, corresponding to$(836\pm 12)\times {10}^6$$e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$events. We search for production of the HNL (denoted$N$) in the decay${\tau }^{-}\to {\pi }^{-}N$followed by its decay via$N\to {\mu }^{+}{\mu }^{-}{\nu }_{\tau }$. The search focuses on the parameter-space region in which the HNL is long-lived, so that the${\mu }^{+}{\mu }^{-}$originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the$\tau$neutrino as a function of the HNL mass.

Published by the American Physical Society2024 

We report a search for the charged-lepton flavor violation in Υ(2S) →ℓ^∓τ^±(ℓ=e, μ) decays using a 25 fb⁻¹Υ(2S) sample collected by the Belle detector at the KEKBe⁺e⁻asymmetric-energy collider. We find no evidence for a signal and set upper limits on the branching fractions ($$ \mathcal{B} $$$B$) at 90% confidence level. We obtain the most stringent upper limits:$$ \mathcal{B} $$$B$(Υ(2S)→ μ^∓τ^±)<0.23×10⁻⁶and$$ \mathcal{B} $$$B$(Υ(2S)→ e^∓τ^±)<1.12×10⁻⁶.