Data from: Age-dependent variation in the terminal investment threshold in male crickets

The terminal investment hypothesis proposes that decreased expectation of
future reproduction (e.g., arising from a threat to survival) should
precipitate increased investment in current reproduction. The level at
which a cue of decreased survival is sufficient to trigger terminal
investment (i.e., the terminal investment threshold) may vary according to
other factors that influence expectation for future reproduction. We test
whether the terminal investment threshold varies with age in male
crickets, using heat-killed bacteria to simulate an immune-inducing
infection. We measured calling effort (a behavior essential for mating)
and hemolymph antimicrobial activity in young and old males across a
gradient of increasing infection cue intensity. There was a significant
interaction between the infection cue and age in their effect on calling
effort, confirming the existence of a dynamic terminal investment
threshold: young males reduced effort at all infection levels, whereas old
males increased effort at the highest levels relative to naïve
individuals. A lack of a corresponding decrease in antibacterial activity
suggests that altered reproductive effort is not traded against investment
in this component of immunity. Collectively, these results support the
existence of a dynamic terminal investment threshold, perhaps accounting
for some of the conflicting evidence in support of terminal investment.