DOI: 10.5061/dryad.rfj6q5774
title: Social hierarchy reveals thermoregulatory trade-offs in response to repeated stressors

description: Coping with stressors can require substantial energetic investment, and
 when resources are limited, such investment can preclude simultaneous
 expenditure on other biological processes. Among endotherms, energetic
 demands of thermoregulation can also be immense, yet our understanding of
 whether a stress response is sufficient to induce changes in
 thermoregulatory investment is limited. Using the black-capped chickadee
 as a model species, we tested a hypothesis that stress-induced changes in
 surface temperature (Ts), a well-documented phenomenon across vertebrates,
 stem from trade-offs between thermoregulation and stress responsiveness.
 Because social subordination is known to constrain access to resources in
 this species, we predicted that Ts and dry heat loss of social
 subordinates, but not social dominants, would fall under stress exposure
 at low ambient temperatures (Ta), and rise under stress exposure at high
 Ta, thus permitting a reduction in total energetic expenditure toward
 thermoregulation. To test our predictions, we exposed four social groups
 of chickadees to repeated stressors and control conditions across a Ta
 gradient (n=30 days/treatment/group), whilst remotely monitoring social
 interactions and Ts. Supporting our hypothesis, we show that: (1) social
 subordinates (n=12), who fed less than social dominants and alone
 experienced stress-induced mass-loss, displayed significantly larger
 changes in Ts following stress exposure than social dominants (n=8), and
 (2) stress-induced changes in Ts significantly increased heat conservation
 at low Ta and heat dissipation at high Ta among social subordinates alone.
 These results suggest that chickadees adjust their thermoregulatory
 strategies during stress exposure when resources are limited by
 ecologically relevant processes.  
description: <strong>## Readme</strong> This
 note contains necessary descriptions for understanding and working with
 data used in the construction of Robertson et al, 2020 (<em>Journal
 of Experimental Biology, </em>223, jeb229047). Below, we list each
 file name attached to this data repository, and descriptions of the data
 contained within each column of a data file if it is a .CSV. Information
 pertaining to our R code (which has been provided in this data repository)
 has not been provided within this readme note, because necessary
 descriptions for understanding our code are provided within the R code
 file itself. <strong>Data
 files:</strong> <strong>1) "All
 Combined Thermal Data.csv".</strong> This
 CSV contains all ambient temperature and surface temperature measurements
 drawn from flight enclosures and individual Black-capped Chickadees
 (respectively) across each day of experimentation. Columns found within
 this data file are as follows: Column 1: Row numbers
 (not used in our analyses, but are residual from previous raw data frames
 that were bound in the construction of this final, master data
 sheet). Column 2: Dates from which ambient temperature
 and surface temperatures found in a row were drawn. Dates are in YYYYMMDD
 format and are treated as factors in our analyses.<br> <br>
 Column 3: The time at which an ambient temperature and surface temperature
 measurement found in a row were drawn, as measured in seconds (integer),
 with second 0 equaling 12:00 AM of a given day. Time was measured in
 seconds as surface temperature measurements were captured at a frequency
 of one frame per second. Column 4: Flight enclosure ID
 (a factor). This column contains the identity of a flight enclosure that
 the individual from which a surface temperature measurements was captured,
 was maintained. This experiment used 20 Black-capped Chickadees that were
 maintained across 4 flight enclosures (labelled by their cardinal
 position, with respect to other flight enclosures). Note that some
 enclosure IDs as labelled with their ID name, followed by "_2";
 such IDs are found on rows that contain surface temperature measurements
 that were captured during a second filming session of that
 individual's enclosure in a given day. Specifically, we rotated our
 thermal imaging camera among flight enclosures each day. If an
 individual's surface temperature was captured during the second
 session of filming, it's respective flight enclosure was labelled,
 "FLIGHTID_2", where "FLIGHTID" is replaced with the
 true identity of the flight enclosure.       <br> <br> Column
 5: Flight enclosure ID abbreviated (a factor). This column contains the
 equivalent data to that described in column 4, however, second filming
 sessions are not labelled as distinct from first filming sessions. The
 enclosure identity column was used for all analyses described in our
 study.<br> <br> Column 6: Maximum surface temperature of the
 eye region of a thermally imaged Black-capped Chickadee, in degrees
 Celsius (a continuous, numeric variable).<br> <br> Column 7:
 Quality of the thermal image from which surface temperature measurements
 contained in column 6 were drawn. Thermal images of individual that were
 captured during movement, and were thus blurry, were labelled "Poor
 Eye", whereas those captured during moments with no movement, and
 were thus in focus, were labelled "Good". Rows containing
 surface temperature measurements that had quality values of "Poor
 Eye" were excluded from our analyses.<br> <br> Column 8:
 Ambient temperature (a continuous, numeric variable) experienced during
 the time at which a surface temperature measurement contained in a given
 row was measured. Ambient temperature values were collected every 5
 minutes, and were assumed to remain constant from the time of collection
 to the second before the next temperature measurement was drawn.<br>
 <br> Column 9: Experimental treatment (a factor). Rows containing
 surface temperature measurements that were captured from individuals
 experiencing control treatments are labelled "Rest", while those
 captured from individuals experiencing stress exposed treatments are
 labelled "Stress".<br> <br> Column 10: Bird identity
 (a factor). The individual from which a surface temperature measurement in
 a given row was collected is identified by it's unique coloured
 leg-band combination here. <strong>2)
 "Digital Bird with RT.csv".</strong>
 This CSV contains data used for analyses of feeding rate and
 social status of our Black-capped Chickadees. It contains surface
 temperature measurements of Chickadees across dates, times, and
 experimental treatments, and contains an enumerated presence and absence
 column for use in feeding rate analyses and social status determination.
 Columns within this data file are as follows: Columns
 1-2: Equivalent to columns 2-3 in "All Combined Thermal
 Data.csv".<br> <br> Column 3: Equivalent to column 4 in
 "All Combined Thermal Data.csv".    <br> <br> Column
 4: Time at which a surface temperature measurement contained within a
 given row was collected, as written in HHMMSS format, rather than absolute
 seconds format. This column is not used in our analyses, and is contained
 for simple visualization purposes.<br> <br> Columns 5-7:
 Equivalent to columns 6-8 in "All Combined Thermal
 Data.csv".<br> <br> Column 8: Equivalent to column 5 in
 "All Combined Thermal Data.csv".    <br> <br> Column
 9: Equivalent to column 9 in "All Combined Thermal Data.csv".  
  <br> <br> Column 10: A duplication of column 1, but with a
 truncated column name for simplicity. Date from which a surface
 temperature measurement in a given row was captured.<br> <br>
 Column 11: Equivalent to column 5 in "All Combined Thermal
 Data.csv".<br> <br> Column 12-16: Columns describing the
 presence (1) or absence (0) of a given individual (defined by the column
 name), at a given second of an experimental day, as defined by columns 1
 and 2 of a given row. This experiment was conducted across 4 flight
 enclosures, with 5 individuals held within each flight enclosure; each
 column therefore pertains to the presence of absence of one specific
 individual in the flight enclosure identified in columns 3 and 11 for a
 given row. Note that the identities of individuals defined in each column,
 with respect to their unique coloured-leg band combinations, are
 identified within the attached r code. Importantly, not all rows
 containing a presence value (1) also have a corresponding surface
 temperature value, because the eye region of birds that were feeding could
 not always be viewed.<br> <br> Column 17: A column defining
 the global presence (1) or absence (0) of any feeding birds (as identified
 in digital video), at any given time.       
 <strong>3) "Effects of Social Status on Stress-induced
 Changes in Surface Temperature of
 Chickadees.R".</strong> This file contains
 all necessary code for reproducing analyses that were conducted in
 Robertson et al (2020; <em>Journal of Experimental Biology,
 </em>223, jeb229047).