% Killer Whales Are Manufacturing Grooming Tools, Mostly With Family % Science Journaling Club, Field Notes % Compile with: pdflatex killer-whale-kelp-tools.tex (twice, for references) \documentclass[11pt]{article} \usepackage[a4paper,margin=1in]{geometry} \usepackage{amsmath} \usepackage{amssymb} \usepackage{booktabs} \usepackage[colorlinks=true,linkcolor=blue,citecolor=blue,urlcolor=blue]{hyperref} \title{Killer Whales Are Manufacturing Grooming Tools, Mostly With Family} \author{The Science Journaling Club} \date{Field Notes --- Paper Analysis} \begin{document} \maketitle \begin{abstract} Between 10 April and 27 July 2024 a drone crew filmed 30 bouts of two southern resident killer whales manipulating a length of bull kelp (\emph{Nereocystis luetkeana}) between their bodies, a behavior Weiss and colleagues name ``allokelping'' \cite{weiss2025}. On 7 of 8 clearly filmed acquisitions the kelp was not found loose but bitten to a short length off an intact, rooted stalk, the ``detach'' mode in the standard taxonomy of animal tool manufacture \cite{shumaker2011}. Bouts ran a median of 1:19 (interquartile range about 81 seconds, maximum 12:04); sustained bodily contact within a bout ran a median of 32 seconds (maximum 3:06). A Bayesian model restricted mostly to J pod (27 of the 30 bouts, 25 individually identified whales) found that partnership was positively predicted by maternal kinship ($\beta \pm \mathrm{SE} = 0.91 \pm 0.21$, posterior $P(\beta>0) > 0.99$) and by age similarity ($P=0.98$), with weaker, tentative support from visible skin moulting ($P=0.93$) and no support at all for a general decline with age ($P=0.53$). We add three numbers of our own, computed directly from the paper's reported effort and counts and labelled as such throughout: a bout rate of roughly 2.90 per hour of drone footage, an average of about 2.15 re-initiations per multi-initiation bout, and nothing else. The paper itself frames its strongest claim, that this is the first confirmed case of tool manufacture in a marine mammal, as conditional on a functional benefit that remains unconfirmed. We keep that hedge intact. \end{abstract} \section{What the Drone Caught} The southern resident killer whale population -- three matrilineal pods, J, K and L, living mostly in the Salish Sea and eating almost exclusively Chinook salmon -- is among the most closely individually tracked wild mammal populations on Earth, numbering 74 animals at NOAA Fisheries' most recent census \cite{noaa2025}. Between 10 April and 27 July 2024, Weiss and colleagues flew a remotely piloted aircraft over all three pods and recorded 30 bouts of two whales sharing a manipulated length of bull kelp stipe \cite{weiss2025}. Solitary whales draping loose kelp over themselves, ``kelping,'' is already a documented and fairly ordinary cetacean behavior \cite{meynecke2023}; what the drone caught was categorically different, involving two animals, a shared object, and a manufacturing step that solitary kelping does not require. \section{Use Versus Manufacture} The tool-use literature the paper itself cites draws a specific line. Tool \emph{use} is applying an unmodified object, found ready to hand, to a job. Tool \emph{manufacture} additionally requires that the user structurally alter the object first \cite{shumaker2011}. A 2013 review of tool use in aquatic animals is the source Weiss and colleagues themselves cite for the framing claim that opens their paper: cetacean tool use is largely restricted to foraging contexts, with no prior report of a cetacean fashioning a tool by modifying an object \cite{mann2013,weiss2025}. Plausibly this is so because ``modify an object'' is a phrase built around hands, and nothing in the water has one. Table \ref{tab:checklist} walks the four components of that definition against what was actually filmed. \begin{table}[h] \centering \caption{Does allokelping clear the manufacture bar? After Shumaker, Walkup \& Beck (2011) \cite{shumaker2011}.} \label{tab:checklist} \begin{tabular}{lll} \toprule Requirement & Status & Basis \\ \midrule Object taken from the environment & met & intact kelp stalk \\ Structurally altered before use & met & bitten to length, ``detach'' mode \\ Applied to a target to do a job & met & rolled against a partner's body \\ The job is a confirmed real benefit & open & authors' own conditional wording \\ \bottomrule \end{tabular} \end{table} The paper's own sentence is explicit about that last row: allokelping ``would be the first case of tool manufacture ... in marine mammals,'' but only ``if a functional benefit of allokelping can be confirmed'' \cite{weiss2025}. The manufacturing step is directly observed. Whether the finished tool does anything measurably useful, as opposed to being a socially learned habit with no established payoff, is the part the authors themselves leave open, and most secondary coverage of this paper dropped that qualifier. \section{How You Make One} Whales fashion a tool by gripping an intact stalk with their teeth near the narrow end of the stipe, close to the holdfast, then using the kelp's own drag in the water together with their body motion and teeth to shear off a short length \cite{weiss2025}. No limb is involved at any point, since odontocetes have none that could hold or bend an object; the entire process runs on mouth, water resistance and momentum. The paper documents 8 clearly filmed acquisitions in total, of which 7 were unambiguous detachments from an intact, rooted stalk. Set against 30 total bouts, that is a reminder that manufacture is fast and often happens out of camera view; the 8 clear cases establish the method, not the origin of every tool used in every bout. \section{What Two Whales Do With It} Once made, the tool is positioned between the bodies of two whales, who roll it back and forth against their skin in sustained contact \cite{weiss2025}. Bout duration -- from positioning to separation -- ran a median of 1 minute 19 seconds (interquartile range roughly 81 seconds, maximum 12 minutes 4 seconds). Sustained skin contact within a bout, a narrower measure, ran a median of 32 seconds (interquartile range roughly 38 seconds, maximum 186 seconds) \cite{weiss2025}. \section{Ruling Out Play} The authors considered and argued against a simpler reading: that this is juvenile object play. None of the standard markers of cetacean object play -- play chases, surface-active leaping, ``keep-away'' games with the object -- accompanied allokelping \cite{weiss2025,hill2017}. The behavior's stereotyped form, repeated consistently across pairs, and its occurrence across every age-sex class rather than clustering in juveniles, are the grounds the authors give for treating it as something other than play. We would put this more cautiously than the paper does: ruling out ``purely play'' does not establish a specific alternative function, which returns to the open row of Table \ref{tab:checklist}. \section{Sampling Effort} Effort was concentrated heavily in J pod: 9 hours of usable drone footage over 11 days, during which 19 of J pod's 25 individually known whales were seen allokelping, spanning all six of the pod's matrilines. K pod contributed 1 hour across 2 days; L pod contributed 21 minutes on a single day \cite{weiss2025}. \section{The Club's Own Arithmetic} Nothing in this section is the paper's. Summing the three pods' footage gives 9~h + 1~h + 21~min = 10~h~21~min = 10.35~h. Dividing the 30 recorded bouts by that total, \begin{equation} \frac{30\ \text{bouts}}{10.35\ \text{h}} \approx 2.90\ \text{bouts per hour}, \end{equation} or one new bout beginning, on average, roughly every 20.7 minutes of drone footage -- a rate of observation, not of underlying behavior, since whales are not allokelping only while a camera happens to be overhead. Separately, the role-switching data below give 28 re-initiations across 13 multi-initiation bouts, \begin{equation} \frac{28\ \text{re-initiations}}{13\ \text{bouts}} \approx 2.15\ \text{per bout}. \end{equation} Both numbers are simple divisions of quantities the paper already reports, kept separate from the paper's own statistics for exactly that reason. \section{Who Grooms Whom} Restricted mostly to J pod (27 of the 30 bouts, 25 individually identified whales), a Bayesian model related the odds of two whales allokelping together to their kinship and relative age \cite{weiss2025}. Maternal kinship was positively associated with partnering, $\beta \pm \mathrm{SE} = 0.91 \pm 0.21$, posterior $P(\beta>0) > 0.99$. Age similarity was almost as strong, posterior probability 0.98. Visible skin moulting showed weaker, ``tentative'' support, posterior probability 0.93. A candidate decline in participation with a whale's own age found no support, posterior probability 0.53, indistinguishable from chance. The kinship and age-similarity results echo earlier work on this same population showing that age and sex, not raw physical association, shape which killer whales interact socially \cite{weiss2021}. \section{Taking Turns} Among bouts with more than one initiation, the initiating role switched between partners in 66\% of them \cite{weiss2025}. Combined with the reciprocal rolling motion itself, that switching argues against one whale simply using the other as a passive surface, and is consistent with mutual-touch bonding rituals documented in primates generally \cite{dunbar2010}. \section{A Guess at Why} Two non-exclusive hypotheses run through the discussion. The bonding reading leans on the kinship and age-similarity results and on a broader primate literature linking mutual touch to relationship maintenance \cite{dunbar2010}. The skin-care reading leans on the moulting correlate and on cetacean precedent: bowhead whales rub against boulders in a behavior called ``rock-nosing,'' plausibly to manage moulting skin \cite{fortune2017}, and captive bottlenose dolphin mothers and calves rub flippers together in a pattern interpreted as body-surface care \cite{sakai2022}. Neither precedent involves manufacture -- a rock is not modified, a flipper is not detached from anything -- but both support mutual contact as a skin-maintenance mechanism independent of any social payoff. The paper does not adjudicate between the two readings, and neither do we. \section{Comparisons in the Literature} The best-known case of cetacean tool \emph{use} is sponge-carrying by some Shark Bay bottlenose dolphins, who wear a marine sponge over the rostrum while foraging over sharp rubble, a behavior transmitted mostly mother to daughter \cite{smolker1997,krutzen2005}. Notably, the paper that first described sponging posed its own title as a question, signalling caution about the tool-use label even from its discoverers \cite{smolker1997}. Sponging clears tool use easily; it does not clear manufacture, since the sponge is selected and worn rather than structurally altered. The closer parallel sits in chimpanzees, observed passing a stripped plant stem to a grooming partner for dental cleaning \cite{mcgrew1973} -- manufacture combined with a social, other-directed target, the same combination that makes Weiss and colleagues' further, hedged claim -- that allokelping ``may be'' the first tool use in a wild animal benefiting two individuals at once -- worth taking seriously \cite{weiss2025}. \section{What Could Take It Away} The paper closes on bull kelp's sensitivity to warming water, noting that its decline in parts of the southern residents' range ``may pose a threat to the persistence of this behavior'' \cite{weiss2025}. The comparison drawn is to northern resident killer whales, a separate population whose well-documented practice of rubbing against smooth pebble beaches is specific enough to particular sites that conservation policy already protects those beaches on its account \cite{ford1989}. The suggestion is that allokelping, if it proves as important to southern residents as beach-rubbing is to northern residents, may eventually warrant comparable habitat protection for bull kelp itself, rather than protection aimed only at the whales. \section{Reproducing the Club's Numbers} The only original computation in this note is the pair of divisions in Section 7: $30/10.35$ and $28/13$. Both are one line of arithmetic on numbers quoted directly from \cite{weiss2025} and are reproduced in full in the text above; no script accompanies this note because no further computation was performed. \begin{thebibliography}{99} \bibitem{weiss2025} Weiss, M. N., John, R. E., Caro-Ruiz, A. M., Ellifrit, D. 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