If a seal's born on a beach, and no one's there to record it, does it make an impact on population estimates? 

We suspect so. 

NOAA scientists work to understand the Hawaiian monk seal population so that we can work toward recovering this species.  Getting accurate data on breeding females and their pups is especially important for calculating reproductive rates and estimating growth potential in the population.  

While the main islands may have relatively few seals, they are home to many monk seal enthusiasts, many of whom report seal sightings to a hotline or even volunteer to monitor seals.  We used this citizen science resource to answer our research questions:

1)  Can sightings records from citizen scientists could help fill in gaps in our reproductive data set?

2) How much do missed pup events impact the reproductive estimates?

NOAA’s Hawaiian Monk Seal Research Program has harnessed this citizen science energy to generate quality data to fill in gaps in monk seal reproductive data.  

• We plotted the sighting histories of individual adult females to identify patterns in their nursing and molting dates that indicated unobserved pupping events.  

• All adult female seals (n=79) sighted from Hawaii Island to Kauai between 1988-2017.

• Observations with pups / nursing (red)

• Observations while molting (blue)

Monk seal mom-pup pairs can be a special sight to see!  Some female seals are seen regularly, and pup in readily noticable locations (like RH58, "Rocky", plotted below), so we have high certainty about their reproductive output. 

However, it can be harder to track the reproductive success of females who are seldom seen or pup in unknown locations.  For these animals, patterns in their sightings (or gaps in sightings) along with molt timing can help detect when we might have missed a pupping event.

• Monk seals typically nurse pups for ~40 days.  So, gaps of over 40 days between sightings (gray lines) could be enough time to miss a pup.

• Monk seals typically molt shortly after (1.5-2 months, light blue line) weaing their pups.

• Monk seals molt at approximiately 1 year intervals, however molts get shifted later in the year after a female undergoes gestation and nursing.  So, staggered patterns in molt timing indicate pupping.

• 25 unobserved pupping events were highly probable
• 132 unobserved pupping events were possible  

When these probable, but unobserved pups are added to our tally of observed pups, we are able to refine our estimated reproductive curves for the main islands seal population.  Accounting for the unobserved pups, boosted the reproductive curves for main islands monk seals.

• Sightings data not only helps track the monk seal population, it helps address crucial questions of monk seal biology.
• Missing pup sightings impact estimates of females reproductive rates and population growth potential.
• Public sightings reports are invaluable in filling data gaps.
• Recording molt data can be especially important.