Mammoth Energy Services, Inc. (TUSK) Ownership
TUSK ownership summary
as of October 18, 2026- Institutions
- 54.0% of shares outstanding
- Insiders
- 15.78% of shares outstanding
- Shares outstanding
- 48.1M
- Float
- 36.0M shares available to trade
- Short interest
- 0.44% 111K shares short
- Days to cover
- 1.24 short interest up 24.4% vs prior month
- Institutions 53.98%
- Insiders 15.78%
- Other investors 30.24%
TUSK top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Wexford Capital LP | 25.08% | 12.1M | $32.7M | −10.0M (−45.3%) | June 30, 2026 |
| 2 | Adage Capital Partners Gp LLC | 9.51% | 4.6M | $12.4M | — | June 30, 2026 |
| 3 | Vanguard Capital Management, LLC | 2.20% | 1.1M | $2.9M | +240,483 (+29.4%) | June 30, 2026 |
| 4 | Peapod Lane Capital LLC | 1.68% | 808K | $2.2M | +207,999 (+34.7%) | June 30, 2026 |
| 5 | Dimensional Fund Advisors, Inc. | 1.44% | 692K | $1.9M | +5,468 (+0.8%) | June 30, 2026 |
| 6 | Jane Street Group LLC | 1.05% | 507K | $1.4M | +483,808 (+2,117.0%) | June 30, 2026 |
| 7 | Citadel Advisors Llc | 0.94% | 452K | $1.2M | +120,796 (+36.5%) | June 30, 2026 |
| 8 | BlackRock Inc | 0.85% | 408K | $1.1M | −1.0M (−72.0%) | June 30, 2026 |
| 9 | Marshall Wace Asset Management Ltd | 0.82% | 396K | $1.1M | +395,583 (0.0%) | June 30, 2026 |
| 10 | The Johns Hopkins University | 0.80% | 387K | $1.0M | +387,359 (0.0%) | June 30, 2026 |
| 11 | Bridgeway Capital Management, LLC | 0.69% | 332K | $898,907 | — | June 30, 2026 |
| 12 | Geode Capital Management, LLC | 0.64% | 306K | $827,806 | −304,898 (−49.9%) | June 30, 2026 |
| 13 | Renaissance Technologies Corp | 0.61% | 292K | $790,617 | +60,308 (+26.0%) | June 30, 2026 |
| 14 | Arrowstreet Capital Limited Partnership | 0.60% | 290K | $784,710 | +290,096 (0.0%) | June 30, 2026 |
| 15 | Empowered Funds, LLC | 0.50% | 241K | $652,752 | — | June 30, 2026 |
| 16 | AQR Capital Management LLC | 0.37% | 178K | $481,014 | +111,093 (+166.5%) | June 30, 2026 |
| 17 | Los Angeles Capital Management LLC | 0.34% | 163K | $441,616 | +163,259 (0.0%) | March 31, 2026 |
| 18 | Vanguard Fiduciary Trust Co | 0.34% | 162K | $437,645 | −8,340 (−4.9%) | June 30, 2026 |
| 19 | Round Rock Advisors, LLC | 0.32% | 153K | $413,435 | +152,841 (0.0%) | June 30, 2026 |
| 20 | Morgan Stanley - Brokerage Accounts | 0.28% | 134K | $361,280 | −19,163 (−12.5%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 12 holders added 2.6M shares and 5 cut 11.4M.
TUSK top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Vanguard MStar Total Stk Mkt Idx Invest | 1.60% | 768K | $2.1M | — | August 31, 2026 |
| 2 | Russell Inv US Small Cap Equity Y | 0.63% | 301K | $814,448 | +161,595 (+115.8%) | August 31, 2026 |
| 3 | EA Bridgeway Omni Small-Cap Value ETF | 0.55% | 265K | $716,224 | — | September 30, 2026 |
| 4 | DFA US Small Cap I | 0.33% | 156K | $423,165 | — | August 31, 2026 |
| 5 | Dimensional US Small Cap ETF | 0.32% | 155K | $418,734 | — | September 30, 2026 |
| 6 | Fidelity Extended Market Index | 0.28% | 137K | $370,796 | +7,697 (+5.9%) | August 31, 2026 |
| 7 | Dunham Small Cap Value N | 0.26% | 124K | $335,764 | +32,856 (+36.0%) | August 31, 2026 |
| 8 | iShares Micro-Cap ETF | 0.23% | 112K | $303,761 | −774 (−0.7%) | September 30, 2026 |
| 9 | DFA US Micro Cap I | 0.19% | 90K | $242,336 | +5,540 (+6.6%) | August 31, 2026 |
| 10 | Russell Inv US Small Cap Equity | 0.14% | 68K | $184,016 | +35,079 (+106.5%) | August 31, 2026 |
| 11 | EA Bridgeway Ultra-Small Company Mkt ETF | 0.12% | 59K | $160,163 | — | September 30, 2026 |
| 12 | Russell Inv Tax-Managed US Mid&Sm Cap S | 0.11% | 55K | $148,350 | — | August 31, 2026 |
| 13 | Fidelity Total Market Index | 0.09% | 41K | $111,635 | — | August 31, 2026 |
| 14 | Fidelity Series Total Market Index | 0.08% | 40K | $107,448 | — | August 31, 2026 |
| 15 | DFA US Small Cap Value I | 0.08% | 38K | $102,628 | — | August 31, 2026 |
| 16 | Fidelity Nasdaq Composite Index | 0.08% | 36K | $98,492 | — | August 31, 2026 |
| 17 | Dimensional US Core Equity 2 ETF | 0.05% | 25K | $68,561 | — | September 30, 2026 |
| 18 | Avantis US Small Cap Equity ETF | 0.05% | 25K | $66,302 | — | September 30, 2026 |
| 19 | Bridgeway Omni Small-Cap Value N | 0.04% | 22K | $58,158 | — | June 30, 2026 |
| 20 | DFA US Core Equity 1 I | 0.04% | 18K | $49,404 | — | August 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
TUSK insider transactions
latest 4| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2025-12-11 | Arthur H Amron | Buy | $1.89 | 10,000 | $18,900 |
| 2025-05-22 | Arthur L Smith | Sell | $2.51 | 20,000 | $50,200 |
| 2025-05-20 | Arthur L Smith | Sell | $2.51 | 50,000 | $125,500 |
| 2025-05-19 | Arthur L Smith | Sell | $2.49 | 15,000 | $37,350 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
TUSK shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns TUSK
Institutional investors own 54.0% of Mammoth Energy Services's shares and insiders 15.78%. The largest holder is Wexford Capital LP with 25.08% of the shares (12.1M), as of June 30, 2026. Among the top 20 institutions, 12 added shares and 5 reduced their stake in the latest filings. Short interest is 0.44% of the float, or 1.24 days of average trading volume. The share count rose 29.0% since 2014.
Related: TUSK key metrics. See the TUSK stock overview for the latest quote and news.
TUSK ownership FAQ
Who owns the most Mammoth Energy Services stock?
The largest shareholders of Mammoth Energy Services are Wexford Capital LP (25.08%), Adage Capital Partners Gp LLC (9.51%), Vanguard Capital Management, LLC (2.20%), Peapod Lane Capital LLC (1.68%), Dimensional Fund Advisors, Inc. (1.44%).
What percentage of Mammoth Energy Services is owned by institutions?
Institutions hold 54.0% of Mammoth Energy Services's shares outstanding; insiders hold 15.78%.
Which funds own Mammoth Energy Services?
The largest fund holders of Mammoth Energy Services are Vanguard MStar Total Stk Mkt Idx Invest (1.60%), Russell Inv US Small Cap Equity Y (0.63%), EA Bridgeway Omni Small-Cap Value ETF (0.55%), DFA US Small Cap I (0.33%), Dimensional US Small Cap ETF (0.32%).
What is Mammoth Energy Services's short interest?
111K shares of Mammoth Energy Services were sold short, 0.44% of the float; at the average daily volume it would take 1.24 days to cover.
Are insiders buying or selling Mammoth Energy Services?
Of the latest 4 reported insider transactions in Mammoth Energy Services (since May 19, 2025), 1 were purchases and 3 were sales.
How many shares of Mammoth Energy Services are outstanding?
Mammoth Energy Services has 48.1M shares outstanding, of which 36.0M are in the public float.