Building extended phenotypes using incomplete environmental information compromises their design and efficiency.

Animals often face high uncertainty regarding their environment, which
might lead to behavioral decisions based on incomplete information. The
consequences of using incomplete information are likely exacerbated for
animals with “sessile” extended phenotypes (nests, webs, traps). However,
such consequences or their fitness implications remain largely unexplored.
We examined how incomplete information about soil properties impacts the
design and prey capture efficiency of conical pit traps in a sit-and-wait
predator, the antlion larvae Myrmeleon crudelis. We experimentally found
that (1) Larvae constructed traps with steeper angles of repose than
expected for the sand substrate, suggesting that they can manipulate the
soil to enhance the trap’s efficiency. (2) When presented with two
different soils (all fine-grain vs fine-grain top and coarse-grain
bottom), larvae built a pit trap in either one, suggesting that they do
not integrate the soil profiles during building. (3) Building traps in
suboptimal coarse-grain soil affected the pit trap design, reduced prey
capture, and triggered pit trap relocation. Hence, our findings
demonstrate that the efficiency of animals' extended phenotypes is
reduced when their location is decided based on incomplete information and
illustrate how they can cope with the consequences of using sub-optimal
structures for prey capture.