DOI: 10.5061/dryad.6k144/1
title: Predator-prey handling times

description: Laboratory-based estimation of the time required for a predator individual to feed (handle) a prey item, as a function of predator and prey identities and sizes, and water temperature.Year - Year in which measurement was made. (Can be ignored.  My methods differed slightly in the earlier years, but I do not expect this to have affected the results.)

Expt/Location - The room in which the experiment was conducted. (Can be ignored.)

Aerated/Flowthrough/Neither - Whether the aquarium was bubbled with air, was part of a flow-through water system, or was just a bucket of water. Aerated for most species, and flow-through for barnacles. (Can be ignored.)

Temperature - The water temperature in which the aquarium was held (in temperature-controlled rooms).  Most are at 10, 14.5, or 18 deg. C. (measured to the nearest 0.5 deg. C).

Container/Individual_# - Coded. e.g., c10-1.  Here "c10" indicates the aquarium id number (i.e. the 10th container).  "c10-1" indicates the first individual to have been placed in that aquarium.   Individuals were replaced with a new individual when the handling time of a feeding event had been well-constrained.   If, however, the handling time of a feeding event had not been well-constrained, the predator was given the opportunity to feed again, sometimes multiple times, until a feeding event had been well-constrained.  The repeated occurrence of the same code indicates such an individual.  The order in which its multiple prey were eaten is indicated by the "Start_1st" date/time column (see later).

Predator - Either Haustrum haustorium or H. scobina

PredSource -location from which the predator was collected.

PredSize - shell length of the predator in mm (+/- 0.1 mm).

Prey - Prey species name

PreySource  - location from which prey individuals were collected.

PreySize - shell length of eaten prey (+/- 0.1 mm). (Missing values indicate individual lost or broken prior to measurement.)

Risselopsis_varia height - For one prey species, Risselopsis varia, it was more accurate to measure its width than its length.  Thus, for this species, PreySize is not its length but rather its width (as measured in the field).  This column provides the additional (though unused) information on it length.

Drilled? - True/False  - Whether or not the predator had drilled through the shell of the prey (see FeedingSurvey data).

Prey_post-consumption_Weight - the weight of each eaten prey's shell remains (in grams)  [I have allometric relationships to determine pre-consumption weight.  This, therefore, allows me to estimate how much tissue was actually consumed.]

with_operculum_or_radula?  - Whether or not the Prey_post-consumption_Weight includes the weight of the prey's operculum or radula.

operc_weight - the weight of the prey's operculum, if the species has one.

est._%_consumed - a visual estimate of the fraction of the prey's tissue that has actually been consumed.  [in previous analyses I have removed observations in which &lt; 80% of prey tissue was actually eaten, assuming that in the field a predator will eat 100% of the tissue.]

leftover_tissue_weight_(dried) - weight of remaining tissue after dessication

Start_1st - The last date/time point at which I had lasted checked the aquarium before a feeding event had begun.

Start_2nd - The first date/time point at which I observed that a feeding event had begun. (see Exact_Start if empty)

Exact_Start - Yes/No - On some occasions that initiation of a feeding event was directly observed.  The exact starting time was therefore known.

End_1st - The last date/time point at which I had checked the aquarium during which feeding was still underway.

End_2nd - The first date/time point at which I observed the feeding event to have ended.

Exact_End - Yes/No - As for Exact_Start

Min_(days) - The amount of elapsed time (in days) between Start_2nd and End_1st.

Max_(days) - The amount of elapsed time between Start_1st and End_2nd.

Midpoint_(days) - Elapsed time midpoint = (Min+Max)/2

Start_+_End_Windows - The total amount of "error" associated with a handling time estimate. (= Start_2nd minus Start_1st)+(End_2nd minus End_1st).

Inverse Window (for Weighting) - Used for weighted-regression to allocate more weight to better constrained handling time estimates (= 1/(0.01+Start_+_End_Window).) 

Both_Start_and_End_within_+/- 2hr24min - TRUE/FALSE - A somewhat arbitrary cutoff point for excluding "poorly" constrained handling times - short enough to seem constrained enough, long enough to not exclude too much data!