DOI: 10.5061/dryad.8931zcs0h
title: Dominance relationships in captive female African lions are ameliorated by oxytocin administration

description: Free-ranging female African lions maintain symmetrical social
 relationships by respecting each other’s “ownership” of valuable food
 items rather than by supplanting subordinates according to well-defined
 dominance hierarchies. However, captivity often skews relationships in
 captive carnivores, whereas oxytocin elicits prosocial effects in
 virtually all mammals.  We therefore investigated whether captive
 female lions demonstrate obvious dominance relationships, and, if so, we
 hypothesized that oxytocin would reduce asymmetries between dominants and
 subordinates. We designed two experimental protocols for investigating
 pairwise relationships.  We first identified dominant individuals
 by performing neutral trials that allowed each female equal opportunity to
 possess the food item.  Second, we performed non-neutral trials
 that biased the opportunity for subordinates to gain possession
 (“ownership”) of the food and thereby determined whether dominants would
 still gain access to the resource. The neutral tests revealed that pairs
 of captive females do display dominance relationships, with one individual
 possessing the resource more than the other. However, in non-neutral
 trials, subordinates behaved less submissively by increasing aggression
 and their possession of the resource after receiving oxytocin compared to
 when they received saline solution.  Our study not only reaffirms
 the social dynamics altered by captivity but also highlights the potential
 for oxytocin to mitigate these disturbances.
description: <strong>Subjects</strong> All
 trials were performed at Lionsrock Sanctuary FOURPAWS, in South Africa,
 between February and October 2023. Procedures were approved by the
 Institutional Animal Care and Use Committee of the University of
 Minnesota, and in accordance with ARRIVE guidelines. All subjects (n=20
 females, 10 pairs) were healthy female adults in prime condition, housed
 in greater than 1 hectare, species-appropriate enclosures, and were
 selected by sanctuary staff based on health and availability. All 20
 female lions were included equally across trials and analyses. No studies
 were performed on females who were lactating, pregnant, or in estrus, and
 no animals in this study were used for breeding purposes. Pairs were
 selected for the study that had been housed amicably together since early
 adolescence or birth (direct levels of relatedness are unclear due to the
 nature of rescues), and all individuals were similar in age and condition
 within each pair. <strong>Trial
 types</strong> Dominance can be characterized as
 monopolization over a resource (Packer et al., 2001). In this study, we
 use food in the form of blocks of raw meat as a resource (meat was
 provided by the sanctuary and was within feeding guidelines for each
 animal). All animals in the study were pre-trained to take meat blocks
 from the researcher at the gate prior to study and two baseline trials
 were performed to habituate the females to the procedure. Asymmetry in
 resource possession and changes in aggression were measured. 
 Trials were conducted to first determine whether dominant
 behaviors were displayed within a pair of females, then to see whether
 oxytocin could mitigate these behaviors. Each trial consisted of a
 two-part test (neutral and non-neutral) and was repeated a total of four
 times (twice with oxytocin treatment and twice with saline control), 10-14
 days apart (differences based on weather conditions).
 <strong>Trial Protocol</strong>
 Treatment (10 IU Oxytocin) or vehicle (saline, as control) was
 administered intranasally 45 minutes prior to trial commencement
 (presentation of resource), and in alternating order across pairs. During
 trials, the female pair was brought to the gate being lured by meat. For
 the neutral trial, the resource (meat) was placed on a stick against the
 fence at an equidistance between the two females, giving them equal
 opportunity to approach and possess the “resource.” This was repeated a
 total of 5 times (except when one female was reluctant to return or
 excessive aggression occurred, then only repeated 3 times as a humane
 endpoint) with greater than 30 seconds between each round to allow for a
 reset. A lioness was considered “dominant” if she monopolized the resource
 at least 60% of the time. This was followed by a non-neutral trial in
 which an additional set of rounds was administered (directly following the
 first set), where the meat was then held closer to the subordinate, as
 determined by the first set, giving the subordinate a chance to reach the
 meat first and claim “ownership.” It was then observed whether the
 dominant female allowed the subordinate to maintain possession, or if they
 overtook the resource regardless of the “ownership” rule observed in
 female lions in the wild. Groups were selected randomly
 to receive OT or saline in alternating order for a total of 4 trials. The
 dose was 10 international units (IUs) of OT (Burkhart et al., 2022).
 Intranasally administered OT bypasses the blood–brain barrier, peaking at
 45 min and lasting ≈ 4 h. (Weisman et al., 2012; Lee et al., 2020). Trials
 therefore commenced 45 minutes post OT administration. Treatments were
 prepared by research assistant, Dubois, so that the researcher, Burkhart,
 was blinded to the treatment in order to control for biasing behavior,
 interpretation, or interaction during trials. All trials were recorded
 using a Gopro Hero 5 and Samsung s20 5G+. Behavior was
 measured during each round to determine dominance as follows: who
 possessed the resource, as well as aggressive vocalizations and physical
 actions. Aggressive encounters were then categorized by severity, 1= brief
 non-contact, 2= brief contact, 3= prolonged contact. A total dominance
 score was calculated as 1 if vocal + 1 if physical + level of aggression.
 Also measured was how many body lengths apart the individuals were while
 resource was consumed, the ultimate body position of the non-possessor,
 and whether the non-possessor retreated. 
 <strong>Statistical analysis</strong>
 <strong>Differences in Resource
 Possession</strong> Successful possession of the
 food resource by dominant vs submissive lions was our primary indicator
 for the presence of dominance hierarchies within pairs. We therefore
 compared the ratio of within-pair resource possession across trials.
 Binomial generalized linear mixed models (GLMMS) were employed using
 “glmer” (R-package lme4) to model the likelihood of dominant and
 submissive individuals to successfully possess the food resource. This
 “possession” likelihood was modeled as a function of treatment (saline or
 oxytocin), dominance (dominant or subordinate individual), and the
 interaction between treatment and dominance. We considered neutral vs
 non-neutral trials as separate tests and ran these data in separate
 models. Pair identity was added as a random effect to allow for
 pair-differences in aggression and dominance.
 <strong>Differences in Aggressive
 Behavior</strong> We explored differences in
 aggressive behavior and intensity across trials using 4 aggression
 metrics, as changes in aggression for both dominant and subordinate
 individuals was a likely mechanism for changes in pair-wise resource
 possession. We first modeled the presence/absence of vocal aggression (1)
 and physical aggression (2) using binomial GLM models, and then modeled
 physical aggression intensity level (3) and total aggression count (4)
 using poisson GLM models. Data from neutral vs non-neutral trials were
 again modeled separately, as was dominance status for easier
 interpretation of effect sizes. All aggression metrics were modeled as a
 function of treatment (saline or oxytocin), with pair identity used as a
 random effect to allow for pair and individual differences in displayed
 aggression.
description: # Dominance relationships in captive female African lions are ameliorated
 by oxytocin administration
 [https://doi.org/10.5061/dryad.8931zcs0h](https://doi.org/10.5061/dryad.8931zcs0h) This dataset includes behavioral measurements taken from pairs of captive female African lions tested for dominant-subordinate relationships during two trial types, neutral and non-neutral, and under two conditions, oxytocin and control. We measured behaviors including possession, body proximity to each other, vocal and physical aggression occurrences, as well as the level of aggression and who initiated the aggressive occurrence. We also measured body position and whether or not the subordinate female retreats during possession. We determined that dominance does exist between female African lions in captivity, regardless of their egalitarian nature in the wild. The researcher was blinded to the treatment, so the pairs were originally separated into groups (included in data), and treatment order was randomized across groups. dom-dominant sub-subordinate pos-possessor of resource (who got the meat) non-possessor (who did not get the meat)  BL- body lengths between two lions  N- Neutral NN- Non-neutral ## Description of the data and file structure This data is in a csv file (Lion_Longform.csv) designed for use in R.  The description of column names is as follows: * Pair: There were 10 pairs of female lions.  - Group: The 10 pairs of lions were randomized into 4 groups (A, B, C, D), which refer to the order and day they were tested on.  * Dominant: this category lists the name of the dominant individual within that test period (who maintained the resource the majority of the time) - Subordinate: this category lists the name of the subordinate individual within that test period (who maintained the resource the majority of the time) * Date: date of test - Treatment day: refers to the order of the day the test was performed (treatments were given in random order, so this denotes an order by day) * Treatment: Either oxytocin or Saline (control) was given. - N_NN: This column refers to whether it was a neutral (N) or non-neutral (NN) test. Neutral tests hold the resource in a position with equal opportunity for possession, where non-neutral tests hold the resource in a position where possession is biased to the subordinate in order to test the ownership rule.  * Round: each test (neutral or non-neutral) has five consecutive rounds, unless excessive aggression or the animal does not return, then only 3 rounds.  - Lion_name: There are two lions per pair, 20 lions total. This category denotes which lion the rest of the columns are referring to for that row. * Dom_Sub: this column states whether the individual who is named in the "name" column was deemed dominant or subordinate for that test (based on majority possession out of 5 rounds). - Pos_NonPos: denotes whether the individual named in that column possessed the resource (ate the piece of meat) * Proximity_BL: this gives the category for the number of body lengths apart the individuals were at the time of possession. The categories were touching (0), &lt;1, 1-3, &gt;3 - Proximity_score: This gives a numerical score correlating to the number of body lengths between the individuals at the time of possession and is scored as 0= touching, 0.5= less than one body length, 1.5= 1-3 body lengths, 5= greater than 3 body lengths  * Boby_Position: This is given for the subordinate only (hence empty cells for dominants) at the time of possession by the dominant - Retreat: This value was given for subordinates only (hence empty cells) and refers to whether they actively turned away from the dominant.  * Vocal_Aggression: 0 denotes no aggression, 1 denotes the presence of vocal aggression - Physical_Agression: 0 denotes no aggression, 1 denotes the presence of physical aggression * Level_Physical_Aggression: 0= no aggression, 1= physical aggression with no contact (ie, biting at without making contact), 2= Physical aggression with brief contact (ie, a slap with the claw), 3= physical aggression with prolonged contact (ie, physical brawl) - Total_Aggression: the total score equals 1 if vocal aggression occurred, plus 1 if physical aggression occurred, plus the total level of physical aggression * Initiated: This refers only to rows where aggression occurs and denotes each individual involved in the occurrence, whether they initiated it or not. All cells are left blank where no aggression occurred.  ## Sharing/Access information There are no other links or other publicly accessible locations of the data.