No abstract

Movement‐based indices such as moves per minute (MPM) and proportion time moving (PTM) are common methodologies to quantify foraging behavior. Hundreds of studies have reported these indices, many without specifying the temporal resolution of their original data, and others using varying resolutions. This was done despite the likelihood that observation resolution can affect MPM and PTM estimates. Our goal was to empirically determine the sensitivity of these foraging indices to changes in the temporal resolution of the observation. We used a high-speed camera to record movement sequences of 20 Acanthodactylus boskianus lizards. Then, we gradually decreased the resolution of the data and calculated the foraging indices at different temporal resolutions. When considering the range of temporal resolutions that are relevant for field observations with unassisted vision, we found 68% and 48% difference in MPM and PTM estimates, respectively. When using the highest resolution, our estimate of MPM was an order of magnitude higher than all prior reported values for lizards. Our results raise major concerns regarding the use of already published movement-based indices, and enable us to recommend how new foraging data should be collected.

New measurement methods can improve the understating and prediction of ecosystem processes. An emerging tool in biogeochemical studies is the coupled measurement of CO 2 and O 2 fluxes. In respiration the ratio CO 2 production/O 2 consumption is termed the "respiratory quotient" (RQ). The inverse term "oxidative ratio" (OR, 1/RQ) is also used, especially when describing ecosystem processes that include photosynthesis with O 2 production (where the fluxes direction is opposite to respiration). Both ratios depend primarily on the stoichiometry, of the respiratory substrate or the net synthesized biomass. The stoichiometry of an organic molecule determines the mean oxidation state (C ox ) of the C atoms in the molecule (LaRowe & Van Cappellen, 2011;Masiello et al., 2008). The more oxidized (higher C ox ) the molecule, the fewer moles of O 2 are consumed per mole of CO 2 released during complete oxidation and the RQ is higher (Table 1). For this reason RQ is often used to infer which

The ratio of CO 2 /O 2 fluxes in respiration (ARQ) depends on the substrate stoichiometry and on additional processes reacting with the gases • Bulk-soil ARQ value is governed by stoichiometry in high respiration rates and by processes like abiotic Fe 2+ oxidation in low rates• ARQ can be used to partition soil respiration sources as shown by distinct bulk-soil and roots ARQ values that confine total soil value