Great stuff - and I cite,
With provisioning occurring 3–4 times per week at the
SRMR and focal individuals consuming an average of ~0.74
heads per provisioning day, we estimate that
these sharks consume ~2.6 provisioned tuna heads per week,
which is similar to our estimate of food required to meet
their weekly energy budget (2.3 heads per week).
As such, it
appears that our focal sharks may be fuelling their energy
requirements exclusively from provisioning. However, considering
that encounter rates vary widely among individuals
and between months and that electronic tracking data show
that individuals intermittently leave the area for a few consecutive
days, weeks to months throughout the year before
returning to the feeding site (Brunnschweiler et al., 2010;
Brunnschweiler & Barnett, 2013), at the most this may only
be the case for some individuals at certain times of the year
(e.g. at the beginning of a calendar year).
....
The foremost limitation to this study is that data and
inferences are based on 10 individuals observed on 36 days.
These 10 individuals may be bolder than other bull sharks
encountered at the SRMR and thus predisposed to take food
and, hence, the patterns found for these individuals may not
reflect all the bull sharks in the area. Given the variable
number of sharks at feeding events and days individuals are
absent from feeding events (Brunnschweiler & Baensch,
2011; Brunnschweiler & Barnett, 2013), further work is
needed to determine the importance of tuna heads compared
with natural prey in bull shark diets, for example, stable isotope
analysis.
So there you have it.
Very surprisingly indeed, those Tuna heads we feed are not at all rubbish but instead a valuable supplement that can help bulk up our Sharks when they come back all exhausted and emaciated after the pupping and birthing season - and I can fully confirm that we've seen many an individual Shark become chubby and happy again after only a few visits!
But what about the potential negative aspects?
Could we be overfeeding them, and could we be subtracting them from the regulatory role they got to play in the environment?
Likely not, as a) the feeding frequency is not uniform but highly individual and determined by individual dominance and/or boldness, b) our observations tell us that those same dominant Bulls do not simply gorge themselves but clearly stop feeding once they got enough and c) our Bull Sharks are not resident but only sporadic visitors whereby individual site fidelity and thus residency is by no means uniform let alone increasing but instead varies greatly from year to year - re-read
this post and paper!
But that's obviously not hard evidence but (highly) educated guess.
Hence the suggestion that one examine the Bull Sharks' diet via e.g. stable isotope analysis - and without wanting to preempt anything, I can state with great confidence that you will need to keep watching this space! :)
Re-read
this: the
actual problem is not the provisioning
per se but the disturbance of the Whitetips' diel rhythm,
and not the fact that they are being fed but instead, the fact that they are not getting enough food and are incurring a metabolic loss as a consequence!
Incidentally,
much like at those cage dives where in their collective wisdom, the regulators have decreed that the GWS must chase teaser baits without ever being fed - and even more so in e.g. Shark Alley where they are being lured into wasting heaps of energy on fruitless breaches so that the photographers can get their shots!
Detail detail!
But I'm digressing as usual.
