Wild kangaroos become more social when caring for young and may maintain long-term affiliations with popular individuals
Data files
Dec 02, 2022 version files 103.26 KB
-
Campbell_Ord_data.xlsx
-
README.md
Sep 07, 2023 version files 103.26 KB
-
Campbell_Ord_data.xlsx
-
README.md
Abstract
Kangaroos are an iconic group of Australian fauna. Despite considerable research on kangaroo behaviour, key gaps remain in our understanding of their social organization in the wild. In particular, it remains largely unknown whether kangaroos form long-term social bonds and what factors might prompt individuals to associate or dissociate from one another. Over 6 years, we monitored the social affiliations of individually identified eastern grey kangaroos, Macropus giganteus, in a large wild population. We investigated the short-term and long-term relationships of kangaroos and the extent those relationships varied with age, sex and reproductive state. We found evidence that long-term relationships among eastern grey kangaroos are possible, especially between adult females. Those individuals that were more sociable within years were also more likely to establish affiliations across years. Contrary to previous studies, we observed females actively associating with other mothers in the years in which they had young. These data suggest that the fission-fusion dynamics of eastern grey kangaroo social behaviour allow females to modulate their social position with conspecifics according to their current reproductive state. We highlight the adaptive implications of the formation of long-term bonds and the changes in social behaviour observed in females.
README: Wild kangaroos become more social when caring for young and may maintain long-term affiliations with popular individuals
MS Authors: Campbell, Nora E; Ord, Terry J
FILE NAME AND CONTENT
Campbell_Ord_data.xlsx
All data used in analyis of kangaroo social networks.
FILE STRUCTURE AND UNITS OF MEASUREMENT
The file is a xlsx file that can be opened using any text, spreadsheet or statistical program.
xlsx file column headings
Descriptions for the headings in the .xlsx file are given below.
Roo
- The individual kangaroo, given by a number, predated by the sex/age it was last seen as. E.g. Roo f4 is kangaroo 004, who was last seen in 2020, identified as a female.
sex
- The sex/age of the focal kangaroo in a given year. Females with and without young are categorised seperately.
Date
- The date that the photograph used to identify the kangaroo was taken.
Time
- The time that the photograph used to identify the kangaroo was taken.
AM/PM
- The time of day the data was collected. AM data was collected shortly after sunrise until mid-morning. PM data was collected from mid-afternoon to sunset.
All other individuals within 3 m
- All other kangaroos seen within an estimated 3 meters of the focal kangaroo.
Males
- The number of males in the photograph with the focal kangaroo.
Females without Young
- The number of females with no young in the photograph with the focal kangaroo.
Females with Young
- The number of mother kangaroos in the photograph with the focal kangaroo.
Fully emerged juveniles
- The number of juveniles belonging to the focal kangaroo (only valid if the focal kangaroo was a female with young), that are fully emerged from the pouch.
Other juveniles
- The number of juveniles not belonging to the focal kangaroo seen in the photograph with the focal kangaroo.
Unknown
- The number of kangaroos in the photograph with the focal kangaroo whose sex cannot be determined.
Observed ID'd Associates
- Individual kangaroos (represented by a number) that are seen in the photograph with the focal kangaroo.
DATA COLLECTOR
- Photographs used in the study were taken by Terry J. Ord. Kangaroos were identified from these photographs by Nora E. Campbell.
Methods
The study was based on identifying individual eastern grey kangaroos from high-resolution digital photographs. These were taken during a systematic annual survey of a wild population on private property near the locality of Wollar in the New South Wales Central Tablelands. This population ranged in size from 34 to 71 individuals. The photographic survey was conducted annually over six years (2015–2020) by the second author and at approximately the same time each year (see below for the exception). The survey was done in the Austral spring, except for 2016 when it took place in winter. Photos were taken using a 200mm lens on a Canon EOS 7D digital SLR from portable hides placed at least 12 hours prior to the first day of observation. The survey was conducted over two to three hours at dawn and again at dusk for three to four consecutive days.
This population of eastern grey kangaroos was particularly suited for this study because individuals rested during the day within a eucalypt woodland surrounding an open grassy valley. At dusk, kangaroos progressively moved out into the grassland of the valley from the woodland to graze and ultimately dispersed out into the surrounding areas around the valley after dark. At dawn, kangaroos would return to the valley to graze until mid-morning and then return to shelter in the eucalypt woodland. This meant hides could be strategically placed around the valley in order to survey virtually all individuals residing in the valley. Hides would be entered at least an hour before dawn and prior to kangaroos returning to the valley, and again at mid-afternoon before kangaroos had left diurnal rest spots inside the eucalypt woodland.
Multiple photos of individuals and their associates were taken to ensure kangaroos could be adequately identified in most instances. Each annual survey typically resulted in a photo library of 500 to 700 images and was considered to be an exhaustive survey of all individuals residing in the valley. In general, a photographic survey is an optimal choice for kangaroos because of its minimal invasiveness (e.g., Austin and Ramp, 2019). Similar survey designs have also been used to take representative ‘snapshots’ of population dynamics in eastern grey kangaroos (Toni et al., 2021) and other animals (Piefke et al., 2021).
Usage notes
Data files can be accessed through Microsoft Excel.