Figure 2. Experience increases hunt rate but decreases total time spent hunting.

Hunting effort of each group is characterized in terms of the distribution in number of hunt events and total hunting duration recorded from the 10 min behavioral recordings. The two test conditions, in the absence and in the presence of prey, are modeled separately to evaluate spontaneous (s) and evoked (e) hunt events, respectively. (A,B,C) Cumulative density function (CDF) of hunt event counts per larva (open squares) reveals that hunt-event frequency increases across groups once prey is added (NF, not-fed; DR, dry-fed; LF, live-fed). Lines indicate 200 cumulative density functions of negative binomial distributions, which have been inferred from hunt-frequency data. (D) Box plots showing number of hunt events per larvae indicate similar spontaneous and evoked counts in each feeding group. Connecting lines indicate that for most larvae the number of hunt events increases on addition of prey. (E) The distribution of estimated mean hunt-rate for each group, as inferred from the models’ parameters, confirms that hunt-rates increase from spontaneous (dotted lines) to evoked (solid lines) conditions. All groups (indicated by line color) show similar mean spontaneous hunt-rates ($R_s$), with a somewhat higher rate observed in NF larvae ($\text{P}[{\mu }_{R_s}^{NF}>{\mu }_{R_s}^{LF}]=0.60$, $\text{P}[{\mu }_{R_s}^{NF}>{\mu }_{R_s}^{DF}]=0.66$). In the presence of prey, however, LF larvae are more likely to exhibit higher hunt-rates than NF and DF larvae ($\text{P}[{\mu }_{R_e}^{LF}>{\mu }_{R_e}^{NF}]=0.72,\text{P}[{\mu }_{R_e}^{LF}>{\mu }_{R_e}^{DF}]=0.75$). Overall, the mean estimated group hunt-rate (events/10 min.) in spontaneous/evoked conditions were ${\mu }_R^{LF}=3.6/14.3$, ${\mu }_R^{NF}=3.8/12.3$, ${\mu }_R^{DF}=3.5/12.0$. (F,G,H) Cumulative function plots showing the total time spent hunting under spontaneous and evoked conditions. Open squares show recorded data and lines indicate 200 cumulative density functions drawn from similar statistical model as in (A,B,C, see Materials and methods). All groups show an increase in total time spent hunting when prey is added. (I) Box plots showing the amount of time spent hunting increases from spontaneous to evoked test conditions for most larvae. (J) The estimated densities of mean hunt-duration of each group, as inferred from the model, clearly show that on average larvae spent more time hunting in evoked conditions (solid lines) than in spontaneous (dotted lines) conditions. Although DF and NF distributions look identical, the model reveals a noticeable shift towards shorter hunt durations (${\displaystyle D}$) for LF larvae on average in both evoked ${\displaystyle (\text{P}[{\mu }_{D_e}^{LF}<{\mu }_{D_e}^{NF}]=0.76,\text{P}[{\mu }_{D_e}^{LF}<{\mu }_{D_e}^{DF}]=0.72)}$ and spontaneous conditions ${\displaystyle (\text{P}[{\mu }_{D_s}^{LF}<{\mu }_{D_e}^{NF}]=0.90,\text{P}[{\mu }_{D_s}^{LF}<{\mu }_{D_e}^{DF}]=0.84)}$.

Figure 2—figure supplement 1. Hunt episode duration shorter in LF group in both spontaneous and evoked hunt events.

(Right) Comparing mean hunt episode durations by fitting a Gamma distribution model to pooled hunt-episode duration data for each group’s spontaneous (dashed) and evoked hunt evens (solid). Hunt episode duration shorter in LF group in both spontaneous ${\displaystyle {\mu }_s^{NF}=2.1,{\mu }_s^{DF}=2.0}$, ${\displaystyle {\mu }_s^{LF}=1.4}$ , with probability $\text{P}[{\mu }_s^{LF}<{\mu }_s^{NF}]=0.80$, $\text{P}[{\mu }_s^{LF}<{\mu }_s^{DF}]=0.75$, and evoked hunt events ${\displaystyle {\mu }_e^{NF}=2.5,{\mu }_e^{DF}=2.3}$, ${\displaystyle {\mu }_e^{LF}=2.0}$, with probability $\text{P}[{\mu }_e^{LF}<{\mu }_e^{NF}]=0.65$, $\text{P}[{\mu }_e^{LF}<{\mu }_e^{DF}]=0.69$. An increase in mean episode duration between spontaneous (no prey) and evoked hunt events is mostly evident in LF and less so in NF hunt events, which are likely to show similar episode durations between conditions ${\displaystyle (\text{P}[{\mu }_e^{NF}>{\mu }_s^{NF}]=0.56)}$. (Left) Kernel density (BW = 0.25 s) estimation using recorded data from spontaneous and evoked hunting events. Distributions across conditions and groups show large overlap in episode duration. 95% of the spontaneous hunt-episode duration data are below 3.5 s. for LF, while this interval includes 78% of NF and 88% of DF. The NF group’s 95% percentile is at 5.02 s. indicating that there are some comparatively longer spontaneous events in this group.

Figure 2—figure supplement 2. Evoked and spontaneous hunt-rates were tested in similar prey density conditions between groups.

CDF of number of detected prey at the beginning of each experiment in both spontaneous ($n=60$ per group) and evoked conditions ($n=60$ per group), shows that measuring evoked hunt-rates in the presence of prey was conducted across similar prey density conditions between groups (NS difference in prey-count between groups using pairwise two-sided t-test, Holm's correction).