DOI: 10.5061/dryad.wdbrv15z8
title: Data from: When rivals are absent: Male aggression towards females in bluefin killifish

description: The process of obtaining mates, mating, and (potentially) caring for
 offspring is costly. While there are inherent costs to reproduction,
 behavioral interactions among individuals are often the primary drivers of
 reproductive costs. Males frequently compete for territories, and females
 may compete for food or males; males often harass females.  Here,
 we sought to determine whether reproductive costs were primarily due to
 male/male competition, female/female competition, or male/female
 interactions in the bluefin killifish. In this species, males guard small
 spawning territories where females visit them daily to spawn. To
 manipulate the potential for male and female competition and male/female
 interactions, we altered the sex ratio and density of each sex across four
 treatments (1 male: 1 female, 1 male : 3 females, 3 males: 1 female, 3
 males: 3 females). Female mortality was higher than male mortality.
 Surprisingly, female mortality and male aggressive behaviors towards
 females (i.e., chases) were highest in treatments with a single male.
 Male-male aggression was present, but males often resolved these disputes
 via signaling by flaring their fins. There was little evidence for overt
 aggression among females. When males lack rivals, they turn their
 territorial defense towards females. These costs help explain why, in
 nature, females promptly leave male territories following spawning and
 join loose shoals with conspecific females and minnows.
description: This experiment aimed to assay the levels of aggression in male
 and female bluefin killifish (both within and between the sexes) and to
 determine the extent to which aggression led to detrimental effects on
 survival. We manipulated the sex ratio and density of bluefin killifish in
 110-liter tanks and observed behavior and survival. We manipulated sex
 ratios and density to create treatments where competition and aggression
 were likely to differ between males and females. We created a treatment
 with a male-biased sex ratio (3 males: 1 female) and a female-biased sex
 ratio (1 male: 3 females). We also had two controls with an even sex ratio
 to control for the density of each sex (1 male : 1 female and 3 males : 3
 females). Six replicates were performed across the four treatments (24
 tanks in total). The experiment was carried out between February 2020 –
 July 2020. The experimental tanks were initially set up in late February
 2020. Due to the COVID-19 pandemic, they remained in those conditions for
 six months. During this time, tanks were censused, fish mortality was
 noted, and dead fish were replaced. We measured survival as the proportion
 of individuals alive in each treatment, which was the total number of
 individuals of each sex alive divided by the total number placed in the
 tank.<strong> </strong> We conducted
 behavioral observations from June - to July 2020. Fish were marked using a
 fluorescent elastomer dye injected underneath their skin, enabling
 individual identification within a tank (Northwest Marine Technology,
 Inc.). Each fish in each tank was observed once for a duration of five
 minutes. During these observations, we recorded the number of chases and
 attacks exhibited by both males and females. The number of fin flares and
 courtship bouts was also noted for males. For chases and attacks, we
 recorded the sex of the recipient of aggression by the focal
 individual. 
description: # When rivals are absent: Male aggression towards females in bluefin
 killifish
 [https://doi.org/10.5061/dryad.wdbrv15z8](https://doi.org/10.5061/dryad.wdbrv15z8) ## Description of the data and file structure Meta-Data for Data Associated with the Article “When Rivals Are Absent: Male Aggression Towards Females in Bluefin Killifish” Explanations for the data in the file “mortality_uploaded.csv”. In this study, we examined the number of males and females that died during the experiment as a function of the different sex ratio and density treatments. We used the following experimental setup – tanks with 1 male: 1 female, 1 male : 3 females, 3 males: 1 female, 3 males: 3 females. The R script ‘mortality_uploaded.R’ refers to these data. * Column 1 Treatment – Sex ratio and density treatments - with 1 male: 1 female, 1 male : 3 females, 3 males: 1 female, 3 males: 3 females - Column 2 Replicate – Replicate number * Column 3 Tank_no - This is the code that was given to each tank of fish. It reflects the treatment and replicate number - Column 4 n_males – Number of Males in the tank as per the treatment * Column 5 n_females – Number of females in the tank as per the treatment - Column 6 N_f_dead – Number of females that died over the course of the experiment * Column 7 N_m_dead – Number of males that died over the course of the experiment - Column 8 total_f_replaced – Number of females that were added into the tank over the course of the experiment, another indication of the number that died * Column 9 total_f_needed – Either 1 or 3, depending on the treatment - Column 10 total_f_used – Original female + any replacement females * Column 11 total_m_replaced - Number of males that were added into the tank over the course of the experiment, another indication of the number that died - Column 12 total_m_needed – Either 1 or 3, depending on the treatment * Column 13 total_m_used - Original female + any replacement males - Explanations for the data in the file “behavior_data_uploaded.csv”. In this study, we examined the male-male, female-female and male-female behavioural interactions as a function of the different sex ratio and density treatments. We used the following experimental setup – tanks with 1 male: 1 female, 1 male : 3 females, 3 males: 1 female, 3 males: 3 females. The R script ‘behavior_data_prep_analysis_uploaded.R’ refers to these data. All rows with common indv_no and tank_no represent the behaviors of an individual. * Column 1 indv_no – Individual ID. This was to ensure that observations were conducted on each individual - Column 2 sex – sex of the individual * Column 3 tank_no - This is the code that was given to each tank of fish. It reflects the treatment and replicate number - Column 4 osr_treatment - Sex ratio and density treatments - with 1 male: 1 female, 1 male : 3 females, 3 males: 1 female, 3 males: 3 females * Column 5 n_males - Number of Males in the tank as per the treatment - Column 6 n_females - Number of females in the tank as per the treatment * Column 7 rep_no - Replicate number - Column 8 date – Date of observation * Column 9 time_of_beh - Time of observation - Column 10 behavior – Behavior displayed by the individual. The ethogram of behaviors is given below: * chasing_m - Focal indv chasing a male - chasing_f - Focal indv chasing a female * chased_by_male – Focal indv chased by a male - fin_flare - fin flare by focal indv * attack_m - Focal indv attacking a male - attack_f - Focal indv attacking a female * being_attacked_by_m - focal indv being attacked by a male Sums of each behavior for each individual was calculated using the summarise() and group_by() functions in the package dplyr and were stored in the data frame ‘holder_data’. This code and the subsequent analysis can be found in the R script ‘behavior_data_prep_analysis_uploaded.R’. ## Code/software All analyses were conducted on R version 4.4.0.